[Users] About forking and unregister

Hi, Anyone know how openser works with following: 1. Forking. Often times, I may have one account register with multiple SIP client, does it support that? I don't seem to make it working. 2. Unregister and register. Nowadays, there are a lot of SIP client will send an Unregister message to the SIP server and after received response, it will send the new registration again, this is because when a client behind the same router reboot multiple times, it might have registration in the SIP server and only the latest one reflect the current registration and all previous registration may not be valid as the router may already close the mapping port, so in RFC3261, it defines client can send a registration with contact head contains "*" and expeiration timer is 0 to unregister the previous registration. It does not seem that OPENSER can handle it. I know SER handles it. 3. Can I specify OPENSER to only send the INVITE (or other SIP request) to the latest AOR for a particular account? Thanks in advance. Bill