yes, the new batter assume the count of the batter he is replacing.
at bat (atbat)
No he or she can not continue batting. Once a player is hit by a pitch, they are automatically given first base and that ends their at bat.
Yes you are. You can even if you have two strikes on you
No. Otherwise you would get this situation: 1) Batter bats a specific side of the plate to get an advantage over pitcher. 2) Pitcher switches pitching hand to negate the advantage. 3) Batter changes side to regain advantage. 4) Repeat steps (2) and (3) ad infinitum. To prevent this, baseball has decided that step (1) is the end of the loop.
His song in the 2011 season was "Let it rock" by Kevin Rudolf. He may change it for the 2012 season but hopefully not!
A pitcher can change his release type as many times as he wants during any atbat. Of course most pitchers don't. If there aren't any baserunners on then he will use the full leg kick to generate the most power. If he has baserunners on the he will use the slide step in order for runners to have less of a jump in case they want to steal. Sometimes you will see a pitcher use the full leg kick with a runner on third base because runners do not usually steal home. Therocket4ever