Question: What triggers the User Equipment (UE) to enter the limited service state over non-3GPP access when a valid USIM is present?
Option 1: Receipt of "5GS services allowed" during registration or service request.
Option 2: Receipt of "PLMN not allowed", "Tracking area not allowed", or "Roaming not allowed in this tracking area" during registration, network-initiated de-registration, or service request.
Option 3: Successful completion of initial registration for non-emergency services.
Option 4: Detection of an "illegal UE" or "illegal ME" when a valid USIM is present.
Explanation: The limited service state over non-3GPP access is triggered when the UE receives specific error messages, such as "PLMN not allowed", "Tracking area not allowed", or "Roaming not allowed in this tracking area", during registration, network-initiated de-registration, or service request. This indicates that the UE is unable to obtain normal service from a PLMN over non-3GPP access due to restrictions imposed by the network.