It is official, and it will definitely make it onto the AH site at some point in the future. However, please feel free to play with any house rules that you like.
No, all combat movement must be completed before any combat begins. The declaration of an amphibious assault with a preceeding naval battle is the only exception.
The most logic and reasonable endgame terms is common sense… you know if (almost certainly) you can’t win, at least experienced players usually does, and probably most AA50 players will already be familiar with AAR or other AA versions.