yes but u ether have to use gameshark or trade pokemon

yes you can but you need an action replay

u can

just use the computer and find a code

U need an action replay to enable any cheats in DS games.There is a cheat where u can get
999 master ball but there is another cheat where u use master balls to get pokemons u want
and the balls are unlimited.

you cant but there is a way if you have pokemon emerald.
there is a cheatwhere u can copy pokemon an just make the pokemon hold a masterball and u
can have alot of pokemon each holding a masterball and each day you can have up to 6
masterballs. hope that helps