Question: What is a requirement for a User Equipment (UE) to be registered in multiple Public Land Mobile Networks (PLMNs) serving networks, either in the same or different PLMNs?
Option 1: The UE must use different subscription credentials for each registration.
Option 2: The UE must establish only one NAS connection with the network.
Option 3: The UE can be registered over both 3GPP and non-3GPP accesses in the same AMF of the same PLMN serving network.
Option 4: The UE is restricted to register in only one type of access (e.g., either 3GPP or non-3GPP).
Explanation: According to the security architecture and procedures for 5G System, a UE can be multiple registered in different PLMNs serving networks or in the same PLMN's serving networks using the same subscription credential(s). This means that the UE does not need to use different credentials for each registration.