Question: What role should a UE acting as a 5G ProSe layer-3 UE-to-network relay support when requesting additional IPv6 prefixes from the SMF?
Option 1: Acting as a "DHCPv4 Server"
Option 2: Acting as an "IPv6 Router"
Option 3: Acting as a "Requesting Router" 
Option 4: Acting as a "Stateless IPv6 Address Autoconfiguration Client"
Explanation: When requesting additional IPv6 prefixes from the SMF, a UE acting as a 5G ProSe layer-3 UE-to-network relay should support acting as a "Requesting Router" to perform procedures described in IETF RFC 8415. This is necessary for the UE to obtain additional IPv6 prefixes beyond the default /64 prefix allocated via stateless IPv6 address autoconfiguration.