Think this has been done before. Anyway I'd say a stalemate. Hulk can't destroy Cell on a Cellular level, but without Planet busting level blasts, Cell can't kill Hulk either and it's questionable even then. Only way I can see it ending is Cell absorbing Hulk, which still would not be easy due to Hulk's brute strength. He'd have to wear Hulk down AND keep his anger from rising for that to work. Maybe Cell wins after days worth of fighting. I don't know. It's either a very difficult win for Cell or a stalemate.
Possibly but it was never shown. I don't think it was chi related though, Dr Gero biologically engineered him. I'd think its akin to Wolverine's biological regeneration which is endless unless completely destroyed. Given that he can regenerate from anything unless every cell is destroyed, I don't think his chi is completely retained in a single cell, hence why I think its biological, otherwise Cell would be just as powerful regardless of of his physical stature.
Been done before, but Cell should still be able to win this fight. He has the advantage in speed and flight plus energy projection. Even though Planet Busting is not allowed Cell can still generate a Blast that can take him out with out destroying the planet. It has been done many times in DB before.