Items can't be imported into Pokemon Black, with perhaps the single exception of using the Relocator to transfer the Mystery Capsule to get the Snarl TM. Apart from that, there's no way to transfer items, items held by pokemon won't be sent across.
You can get 2 Master Balls in both versions.
You don't.
you can trade a Pokemon from black or white holding a master ball.
you trade 100 times
you can't
hack the game
In skyrim
Ar code
poke transfer
You can most likely use cheat codes, to obtain more Master balls, but that requires the action replay, and or (Game Shark?)....
action replay codes
the professor will give it to you after you have beaten the 8th gym.