1) Demons, mages, sacred units, and upkeep-free summons. But many different army compositions are viable.
2) No, not with humans, anyway.
3) Find MP games in this forum, or at
www.dominionsx.com
4) Forever, unless you arrange fast turns ahead of time.
5) Kind of. Search to find the thread...
6) Some maps have fixed or spcified start locations.