Question: What happens when the network receives an ATTACH REQUEST message before completing a network-initiated detach procedure with detach type "re-attach not required" and no EMM cause IE?
Option 1: The network sends a DETACH ACCEPT message to the UE.
Option 2: The network ignores the ATTACH REQUEST message.
Option 3: The network progresses both procedures after deleting EPS bearer context(s).
Option 4: The network changes to state EMM-DEREGISTERED.
Explanation: According to the text, if the network receives an ATTACH REQUEST message before completing a network-initiated detach procedure with detach type "re-attach not required" and no EMM cause IE, or "re-attach not required" and the EMM cause value not #2 "IMSI unknown in HSS", the network shall ignore the ATTACH REQUEST message.