Question: When is the Unified Access Control procedure not applicable to an L2 U2N Relay UE?
Option 1: When the L2 U2N Relay UE initiates RRC connection establishment or RRC connection resume upon reception of any message from a L2 U2N remote UE via SL-RLC0 or SL-RLC1.
Option 2: When the L2 U2N Relay UE is in RRC_IDLE state.
Option 3: When the L2 U2N Relay UE has obtained SIB1 from the target cell after a PCell change in RRC_CONNECTED.
Option 4: When the L2 U2N Relay UE is performing an access attempt associated with a given Access Category and one or more Access Identities.
Explanation: According to the text, the Unified Access Control procedure does not apply to L2 U2N Relay UE initiating RRC connection establishment or RRC connection resume upon reception of any message from a L2 U2N remote UE via SL-RLC0 or SL-RLC1. This is because in such cases, the UE may not have obtained SIB1 from the target cell, which is required for access barring checks.