Play against a human.

1. Duel – 20-40 minutes. I haven't played Skirmish, but I assume that a game on a small map takes about 2-4 hours, and on a large map – 6-8 hours. 2. In "Heroes 6", the maximum number of players is 12, but I haven't seen such maps, so it's up to eight. As for "how many usually" – I don't know. 3. In a duel – immediately 30, in a regular game – as in a game against AI. 4. There are no cheats for "Heroes 6". Unless you consider the weapons of the Dynasty as cheats, of course. 5. It seems that the bug with luck was fixed in patch 1.2.