Heroes in Heroes of Might and Magic V: graphics, biographies, skills...

1. It hasn't been announced. But based on the beta, it's 8-9.
2. One Castle corresponds to 1 hero class. In the beta, the difference between them is only in special abilities. It gives what it wants. So, by level 12, my Warlock hadn't invested a single point in spell power. Instead, he invested in attack and defense.