Will tokens regenerate?
Yes because regenerate prevents creatures from changing zones. They simply tap and are removed from combat, with all combat damage removed from them. Tokens are only destroyed when zones are changed, so undying or persist would not save a token, while regenerate works the same as on any nontoken creatures.
did not think regenerating caused to tap. didnt see it in the rules o.O
other than that, above poster is correct. I second his explanation
Only combat damage? Or all damage?
Any damage, though I'm unclear on damage coming from a card with wither or infect...