diff --git a/README.md b/README.md
index 9e5d7dc428..1ae37766f4 100644
--- a/README.md
+++ b/README.md
@@ -46,6 +46,7 @@ The merge is still actively in development. The exact specification has not been
   * [Fork Choice changes](specs/merge/fork-choice.md)
   * [Validator additions](specs/merge/validator.md)
   * [Client settings](specs/merge/client-settings.md)
+  * [P2P Networking](specs/merge/p2p-interface.md)
 
 ### Sharding
 
diff --git a/specs/altair/beacon-chain.md b/specs/altair/beacon-chain.md
index dbd3e63683..b22f89a4db 100644
--- a/specs/altair/beacon-chain.md
+++ b/specs/altair/beacon-chain.md
@@ -689,7 +689,7 @@ def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
                                       eth1_timestamp: uint64,
                                       deposits: Sequence[Deposit]) -> BeaconState:
     fork = Fork(
-        previous_version=GENESIS_FORK_VERSION,
+        previous_version=ALTAIR_FORK_VERSION,  # [Modified in Altair] for testing only
         current_version=ALTAIR_FORK_VERSION,  # [Modified in Altair]
         epoch=GENESIS_EPOCH,
     )
diff --git a/specs/merge/beacon-chain.md b/specs/merge/beacon-chain.md
index 56476cedd1..b3d1848552 100644
--- a/specs/merge/beacon-chain.md
+++ b/specs/merge/beacon-chain.md
@@ -13,7 +13,6 @@
 - [Constants](#constants)
   - [Execution](#execution)
 - [Configuration](#configuration)
-  - [Genesis testing settings](#genesis-testing-settings)
   - [Transition settings](#transition-settings)
 - [Containers](#containers)
   - [Extended containers](#extended-containers)
@@ -71,15 +70,6 @@ This patch adds transaction execution to the beacon chain as part of the Merge f
 
 ## Configuration
 
-### Genesis testing settings
-
-*Note*: These configuration settings do not apply to the mainnet and are utilized only by pure Merge testing.
-
-| Name | Value |
-| - | - |
-| `GENESIS_GAS_LIMIT` | `uint64(30000000)` (= 30,000,000) |
-| `GENESIS_BASE_FEE_PER_GAS` | `Bytes32('0x00ca9a3b00000000000000000000000000000000000000000000000000000000')` (= 1,000,000,000) |
-
 ### Transition settings
 
 | Name | Value |
@@ -257,7 +247,7 @@ The Engine API may be used to implement them with an external execution engine.
 ```python
 def execute_payload(self: ExecutionEngine, execution_payload: ExecutionPayload) -> bool:
     """
-    Returns ``True`` iff ``execution_payload`` is valid with respect to ``self.execution_state``.
+    Return ``True`` if and only if ``execution_payload`` is valid with respect to ``self.execution_state``.
     """
     ...
 ```
@@ -354,15 +344,21 @@ def process_execution_payload(state: BeaconState, payload: ExecutionPayload, exe
 ## Testing
 
 *Note*: The function `initialize_beacon_state_from_eth1` is modified for pure Merge testing only.
-
-*Note*: The function `initialize_beacon_state_from_eth1` is modified: (1) using `MERGE_FORK_VERSION` as the current fork version, (2) utilizing the Merge `BeaconBlockBody` when constructing the initial `latest_block_header`, and (3) initialize `latest_execution_payload_header`.
+Modifications include:
+1. Use `MERGE_FORK_VERSION` as the current fork version.
+2. Utilize the Merge `BeaconBlockBody` when constructing the initial `latest_block_header`.
+3. Initialize `latest_execution_payload_header`.
+  If `execution_payload_header == ExecutionPayloadHeader()`, then the Merge has not yet occurred.
+  Else, the Merge starts from genesis and the transition is incomplete.
 
 ```python
 def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
                                       eth1_timestamp: uint64,
-                                      deposits: Sequence[Deposit]) -> BeaconState:
+                                      deposits: Sequence[Deposit],
+                                      execution_payload_header: ExecutionPayloadHeader=ExecutionPayloadHeader()
+                                      ) -> BeaconState:
     fork = Fork(
-        previous_version=GENESIS_FORK_VERSION,
+        previous_version=MERGE_FORK_VERSION,  # [Modified in Merge] for testing only
         current_version=MERGE_FORK_VERSION,  # [Modified in Merge]
         epoch=GENESIS_EPOCH,
     )
@@ -397,12 +393,9 @@ def initialize_beacon_state_from_eth1(eth1_block_hash: Bytes32,
     state.current_sync_committee = get_next_sync_committee(state)
     state.next_sync_committee = get_next_sync_committee(state)
 
-    # [New in Merge] Initialize the execution payload header (with block number set to 0)
-    state.latest_execution_payload_header.block_hash = eth1_block_hash
-    state.latest_execution_payload_header.timestamp = eth1_timestamp
-    state.latest_execution_payload_header.random = eth1_block_hash
-    state.latest_execution_payload_header.gas_limit = GENESIS_GAS_LIMIT
-    state.latest_execution_payload_header.base_fee_per_gas = GENESIS_BASE_FEE_PER_GAS
+    # [New in Merge] Initialize the execution payload header
+    # If empty, will initialize a chain that has not yet gone through the Merge transition
+    state.latest_execution_payload_header = execution_payload_header
 
     return state
 ```
diff --git a/tests/core/pyspec/eth2spec/VERSION.txt b/tests/core/pyspec/eth2spec/VERSION.txt
index 9084fa2f71..524cb55242 100644
--- a/tests/core/pyspec/eth2spec/VERSION.txt
+++ b/tests/core/pyspec/eth2spec/VERSION.txt
@@ -1 +1 @@
-1.1.0
+1.1.1
diff --git a/tests/core/pyspec/eth2spec/test/altair/merkle/test_single_proof.py b/tests/core/pyspec/eth2spec/test/altair/merkle/test_single_proof.py
index f9aa68adda..31cdd13bb1 100644
--- a/tests/core/pyspec/eth2spec/test/altair/merkle/test_single_proof.py
+++ b/tests/core/pyspec/eth2spec/test/altair/merkle/test_single_proof.py
@@ -1,12 +1,11 @@
 from eth2spec.test.context import (
     spec_state_test,
-    with_phases,
+    with_altair_and_later,
 )
-from eth2spec.test.helpers.constants import ALTAIR
 from eth2spec.test.helpers.merkle import build_proof
 
 
-@with_phases([ALTAIR])
+@with_altair_and_later
 @spec_state_test
 def test_next_sync_committee_merkle_proof(spec, state):
     yield "state", state
@@ -25,7 +24,7 @@ def test_next_sync_committee_merkle_proof(spec, state):
     )
 
 
-@with_phases([ALTAIR])
+@with_altair_and_later
 @spec_state_test
 def test_finality_root_merkle_proof(spec, state):
     yield "state", state
diff --git a/tests/core/pyspec/eth2spec/test/altair/unittests/networking/test_networking.py b/tests/core/pyspec/eth2spec/test/altair/unittests/networking/test_networking.py
index 37d50611dc..6d9dca5237 100644
--- a/tests/core/pyspec/eth2spec/test/altair/unittests/networking/test_networking.py
+++ b/tests/core/pyspec/eth2spec/test/altair/unittests/networking/test_networking.py
@@ -1,6 +1,6 @@
 from eth2spec.test.context import (
-    with_altair_and_later,
     spec_state_test,
+    with_altair_and_later,
 )
 from eth2spec.test.helpers.state import (
     transition_to,
diff --git a/tests/core/pyspec/eth2spec/test/altair/unittests/test_config_invariants.py b/tests/core/pyspec/eth2spec/test/altair/unittests/test_config_invariants.py
index 4443f97e0b..91be0a0a61 100644
--- a/tests/core/pyspec/eth2spec/test/altair/unittests/test_config_invariants.py
+++ b/tests/core/pyspec/eth2spec/test/altair/unittests/test_config_invariants.py
@@ -1,11 +1,10 @@
 from eth2spec.test.context import (
     spec_state_test,
-    with_phases,
+    with_altair_and_later,
 )
-from eth2spec.test.helpers.constants import ALTAIR
 
 
-@with_phases([ALTAIR])
+@with_altair_and_later
 @spec_state_test
 def test_weight_denominator(spec, state):
     assert (
@@ -17,7 +16,7 @@ def test_weight_denominator(spec, state):
     ) == spec.WEIGHT_DENOMINATOR
 
 
-@with_phases([ALTAIR])
+@with_altair_and_later
 @spec_state_test
 def test_inactivity_score(spec, state):
     assert spec.config.INACTIVITY_SCORE_BIAS <= spec.config.INACTIVITY_SCORE_RECOVERY_RATE
diff --git a/tests/core/pyspec/eth2spec/test/altair/unittests/test_sync_protocol.py b/tests/core/pyspec/eth2spec/test/altair/unittests/test_sync_protocol.py
index c69957de53..15444df819 100644
--- a/tests/core/pyspec/eth2spec/test/altair/unittests/test_sync_protocol.py
+++ b/tests/core/pyspec/eth2spec/test/altair/unittests/test_sync_protocol.py
@@ -1,17 +1,14 @@
 from eth2spec.test.context import (
     spec_state_test,
     with_presets,
-    with_phases,
+    with_altair_and_later,
 )
 from eth2spec.test.helpers.attestations import next_epoch_with_attestations
 from eth2spec.test.helpers.block import (
     build_empty_block,
     build_empty_block_for_next_slot,
 )
-from eth2spec.test.helpers.constants import (
-    ALTAIR,
-    MINIMAL,
-)
+from eth2spec.test.helpers.constants import MINIMAL
 from eth2spec.test.helpers.state import (
     next_slots,
     state_transition_and_sign_block,
@@ -22,7 +19,7 @@
 from eth2spec.test.helpers.merkle import build_proof
 
 
-@with_phases([ALTAIR])
+@with_altair_and_later
 @spec_state_test
 def test_process_light_client_update_not_updated(spec, state):
     pre_snapshot = spec.LightClientSnapshot(
@@ -81,7 +78,7 @@ def test_process_light_client_update_not_updated(spec, state):
     assert store.snapshot == pre_snapshot
 
 
-@with_phases([ALTAIR])
+@with_altair_and_later
 @spec_state_test
 @with_presets([MINIMAL], reason="too slow")
 def test_process_light_client_update_timeout(spec, state):
@@ -147,7 +144,7 @@ def test_process_light_client_update_timeout(spec, state):
     assert store.snapshot.header == update.header
 
 
-@with_phases([ALTAIR])
+@with_altair_and_later
 @spec_state_test
 @with_presets([MINIMAL], reason="too slow")
 def test_process_light_client_update_finality_updated(spec, state):
diff --git a/tests/core/pyspec/eth2spec/test/context.py b/tests/core/pyspec/eth2spec/test/context.py
index ef92efaded..6062648d60 100644
--- a/tests/core/pyspec/eth2spec/test/context.py
+++ b/tests/core/pyspec/eth2spec/test/context.py
@@ -463,8 +463,8 @@ def is_post_merge(spec):
     return spec.fork not in FORKS_BEFORE_MERGE
 
 
-with_altair_and_later = with_phases([ALTAIR, MERGE])
-with_merge_and_later = with_phases([MERGE])  # TODO: include sharding when spec stabilizes.
+with_altair_and_later = with_all_phases_except([PHASE0])
+with_merge_and_later = with_all_phases_except([PHASE0, ALTAIR])
 
 
 def only_generator(reason):
diff --git a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
index 0d03447a76..59308e102a 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/execution_payload.py
@@ -3,7 +3,7 @@ def build_empty_execution_payload(spec, state, randao_mix=None):
     Assuming a pre-state of the same slot, build a valid ExecutionPayload without any transactions.
     """
     latest = state.latest_execution_payload_header
-    timestamp = spec.compute_time_at_slot(state, state.slot)
+    timestamp = spec.compute_timestamp_at_slot(state, state.slot)
     empty_txs = spec.List[spec.Transaction, spec.MAX_TRANSACTIONS_PER_PAYLOAD]()
 
     if randao_mix is None:
diff --git a/tests/core/pyspec/eth2spec/test/helpers/genesis.py b/tests/core/pyspec/eth2spec/test/helpers/genesis.py
index 0e9af4cff9..cd96c8168f 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/genesis.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/genesis.py
@@ -20,6 +20,25 @@ def build_mock_validator(spec, i: int, balance: int):
     )
 
 
+def get_sample_genesis_execution_payload_header(spec,
+                                                eth1_block_hash=None):
+    if eth1_block_hash is None:
+        eth1_block_hash = b'\x55' * 32
+    return spec.ExecutionPayloadHeader(
+        parent_hash=b'\x30' * 32,
+        coinbase=b'\x42' * 20,
+        state_root=b'\x20' * 32,
+        receipt_root=b'\x20' * 32,
+        logs_bloom=b'\x35' * spec.BYTES_PER_LOGS_BLOOM,
+        random=eth1_block_hash,
+        block_number=0,
+        gas_limit=30000000,
+        base_fee_per_gas=spec.Bytes32('0x00ca9a3b00000000000000000000000000000000000000000000000000000000'),
+        block_hash=eth1_block_hash,
+        transactions_root=spec.Root(b'\x56' * 32),
+    )
+
+
 def create_genesis_state(spec, validator_balances, activation_threshold):
     deposit_root = b'\x42' * 32
 
@@ -76,9 +95,9 @@ def create_genesis_state(spec, validator_balances, activation_threshold):
 
     if spec.fork not in FORKS_BEFORE_MERGE:
         # Initialize the execution payload header (with block number and genesis time set to 0)
-        state.latest_execution_payload_header.block_hash = eth1_block_hash
-        state.latest_execution_payload_header.random = eth1_block_hash
-        state.latest_execution_payload_header.gas_limit = spec.GENESIS_GAS_LIMIT
-        state.latest_execution_payload_header.base_fee_per_gas = spec.GENESIS_BASE_FEE_PER_GAS
+        state.latest_execution_payload_header = get_sample_genesis_execution_payload_header(
+            spec,
+            eth1_block_hash=eth1_block_hash,
+        )
 
     return state
diff --git a/tests/core/pyspec/eth2spec/test/merge/genesis/__init__.py b/tests/core/pyspec/eth2spec/test/merge/genesis/__init__.py
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/tests/core/pyspec/eth2spec/test/merge/genesis/test_initialization.py b/tests/core/pyspec/eth2spec/test/merge/genesis/test_initialization.py
new file mode 100644
index 0000000000..78462263b2
--- /dev/null
+++ b/tests/core/pyspec/eth2spec/test/merge/genesis/test_initialization.py
@@ -0,0 +1,122 @@
+from eth2spec.test.context import (
+    MERGE,
+    single_phase,
+    spec_test,
+    with_presets,
+    with_phases,
+    with_merge_and_later,
+)
+from eth2spec.test.helpers.constants import MINIMAL
+from eth2spec.test.helpers.deposits import (
+    prepare_full_genesis_deposits,
+)
+from eth2spec.test.helpers.genesis import (
+    get_sample_genesis_execution_payload_header,
+)
+
+
+def eth1_init_data(eth1_block_hash, eth1_timestamp):
+    yield 'eth1', {
+        'eth1_block_hash': '0x' + eth1_block_hash.hex(),
+        'eth1_timestamp': int(eth1_timestamp),
+    }
+
+
+@with_phases([MERGE])
+@spec_test
+@single_phase
+@with_presets([MINIMAL], reason="too slow")
+def test_initialize_pre_transition_no_param(spec):
+    deposit_count = spec.config.MIN_GENESIS_ACTIVE_VALIDATOR_COUNT
+    deposits, deposit_root, _ = prepare_full_genesis_deposits(
+        spec,
+        spec.MAX_EFFECTIVE_BALANCE,
+        deposit_count,
+        signed=True,
+    )
+
+    eth1_block_hash = b'\x12' * 32
+    eth1_timestamp = spec.config.MIN_GENESIS_TIME
+
+    yield from eth1_init_data(eth1_block_hash, eth1_timestamp)
+    yield 'deposits', deposits
+
+    # initialize beacon_state *without* an execution_payload_header
+    yield 'execution_payload_header', 'meta', False
+    state = spec.initialize_beacon_state_from_eth1(eth1_block_hash, eth1_timestamp, deposits)
+
+    assert not spec.is_merge_complete(state)
+
+    yield 'state', state
+
+
+@with_merge_and_later
+@spec_test
+@single_phase
+@with_presets([MINIMAL], reason="too slow")
+def test_initialize_pre_transition_empty_payload(spec):
+    deposit_count = spec.config.MIN_GENESIS_ACTIVE_VALIDATOR_COUNT
+    deposits, deposit_root, _ = prepare_full_genesis_deposits(
+        spec,
+        spec.MAX_EFFECTIVE_BALANCE,
+        deposit_count,
+        signed=True,
+    )
+
+    eth1_block_hash = b'\x12' * 32
+    eth1_timestamp = spec.config.MIN_GENESIS_TIME
+
+    yield from eth1_init_data(eth1_block_hash, eth1_timestamp)
+    yield 'deposits', deposits
+
+    # initialize beacon_state *with* an *empty* execution_payload_header
+    yield 'execution_payload_header', 'meta', True
+    execution_payload_header = spec.ExecutionPayloadHeader()
+    state = spec.initialize_beacon_state_from_eth1(
+        eth1_block_hash,
+        eth1_timestamp,
+        deposits,
+        execution_payload_header=execution_payload_header,
+    )
+
+    assert not spec.is_merge_complete(state)
+
+    yield 'execution_payload_header', execution_payload_header
+
+    yield 'state', state
+
+
+@with_merge_and_later
+@spec_test
+@single_phase
+@with_presets([MINIMAL], reason="too slow")
+def test_initialize_post_transition(spec):
+    deposit_count = spec.config.MIN_GENESIS_ACTIVE_VALIDATOR_COUNT
+    deposits, deposit_root, _ = prepare_full_genesis_deposits(
+        spec,
+        spec.MAX_EFFECTIVE_BALANCE,
+        deposit_count,
+        signed=True,
+    )
+
+    eth1_block_hash = b'\x12' * 32
+    eth1_timestamp = spec.config.MIN_GENESIS_TIME
+
+    yield from eth1_init_data(eth1_block_hash, eth1_timestamp)
+    yield 'deposits', deposits
+
+    # initialize beacon_state *with* an execution_payload_header
+    yield 'execution_payload_header', 'meta', True
+    genesis_execution_payload_header = get_sample_genesis_execution_payload_header(spec)
+    state = spec.initialize_beacon_state_from_eth1(
+        eth1_block_hash,
+        eth1_timestamp,
+        deposits,
+        execution_payload_header=genesis_execution_payload_header,
+    )
+
+    yield 'execution_payload_header', genesis_execution_payload_header
+
+    assert spec.is_merge_complete(state)
+
+    yield 'state', state
diff --git a/tests/formats/genesis/initialization.md b/tests/formats/genesis/initialization.md
index 73630de51c..d0d453e5b6 100644
--- a/tests/formats/genesis/initialization.md
+++ b/tests/formats/genesis/initialization.md
@@ -17,8 +17,9 @@ eth1_timestamp: int       -- An integer. The timestamp of the block, in seconds.
 A yaml file to help read the deposit count:
 
 ```yaml
-description: string    -- Optional. Description of test case, purely for debugging purposes.
-deposits_count: int    -- Amount of deposits.
+description: string             -- Optional. Description of test case, purely for debugging purposes.
+deposits_count: int             -- Amount of deposits.
+execution_payload_header: bool  -- `execution_payload_header` field is filled or not. If `true`, `execution_payload_header.ssz_snappy` file exists.
 ```
 
 ### `deposits_<index>.ssz_snappy`
@@ -26,11 +27,16 @@ deposits_count: int    -- Amount of deposits.
 A series of files, with `<index>` in range `[0, deposits_count)`. Deposits need to be processed in order.
 Each file is a SSZ-snappy encoded `Deposit` object.
 
+###  `execution_payload_header.ssz_snappy`
+
+*Note*: Param added only for the Merge and subsequent forks.
+
+The execution payload header that state is initialized with. An SSZ-snappy encoded `BeaconState` object.
+
 ###  `state.ssz_snappy`
 
 The expected genesis state. An SSZ-snappy encoded `BeaconState` object.
 
-
 ## Processing
 
 To process this test, build a genesis state with the provided `eth1_block_hash`, `eth1_timestamp` and `deposits`:
diff --git a/tests/generators/genesis/main.py b/tests/generators/genesis/main.py
index 1f36afd4b9..a595db6120 100644
--- a/tests/generators/genesis/main.py
+++ b/tests/generators/genesis/main.py
@@ -9,7 +9,12 @@
     ]}
     altair_mods = phase_0_mods
     # we have new unconditional lines in `initialize_beacon_state_from_eth1` and we want to test it
-    merge_mods = altair_mods
+    merge_mods = {
+        **{key: 'eth2spec.test.merge.genesis.test_' + key for key in [
+            'initialization',
+        ]},
+        **altair_mods,
+    }
     all_mods = {
         PHASE0: phase_0_mods,
         ALTAIR: altair_mods,
diff --git a/tests/generators/merkle/main.py b/tests/generators/merkle/main.py
index 7203c5f193..44fbec10c6 100644
--- a/tests/generators/merkle/main.py
+++ b/tests/generators/merkle/main.py
@@ -1,4 +1,4 @@
-from eth2spec.test.helpers.constants import ALTAIR
+from eth2spec.test.helpers.constants import ALTAIR, MERGE
 from eth2spec.gen_helpers.gen_from_tests.gen import run_state_test_generators
 
 
@@ -6,9 +6,11 @@
     altair_mods = {key: 'eth2spec.test.altair.merkle.test_' + key for key in [
         'single_proof',
     ]}
+    merge_mods = altair_mods
 
     all_mods = {
-        ALTAIR: altair_mods
+        ALTAIR: altair_mods,
+        MERGE: merge_mods,
     }
 
     run_state_test_generators(runner_name="merkle", all_mods=all_mods)