Question: What happens to the existing current 5G security context in the AMF when a UE uses a non-current 5G NAS security context for a NAS Registration Request?
Option 1: The existing current 5G security context is updated with the new 5G NAS security context.
Option 2: The existing current 5G security context is deleted and replaced with the used 5G NAS security context.
Option 3: The existing current 5G security context remains unchanged, and a new 5G NAS security context is created.
Option 4: The AMF sends an error message to the UE indicating that the 5G NAS security context is not valid.
Explanation: According to the text, when a UE uses a non-current 5G NAS security context for a NAS Registration Request, the AMF shall delete any existing current 5G security context and make the used 5G security context the current 5G security context. This ensures that the AMF and UE are using the same 5G NAS security context for further communication.