There will be an official game mode pack that will come with the server, just as there was an official race map pack with the Race release.
You can run any number of scripts at the same time, so yes.
That isn't true. The MTA team isn't making any scripts, the QA team is. The release depends upon the state of the mod itself, not on the scripts. If the mod was finished and there were no completed scripts, it would probably just release without them.