1. Contest currently available depends on you. The game isn't dependant on speed. Casually I'd say 100+ hours. Hardcore? Perhaps 40 or so.

2. Also dependant on you as a gamer. Procedurally generated worlds.

3. It's an EA game with a very small indie team, so not often. In a year so far....1 major patch, since new weapons and enemies here and there. Lots of bug fixes ( main delay imo).

4. Probably a year or two more to go.