If you have already caught them and saved, you cannot re-battle them again. If you made them faint, you have to battle the Elite Four again to make them respawn.
They are Dialga, Palkia, and probably Giratina
You cant!
no you cant with giratina in origin form either
you cant
you cant
You cant
sadly, no. legendaries cant breed.
you cant but you can in explorers of the sky by getting giratina's special orb
If you saved it before you battled it, Turn the game off and battle it again. If you saved it after you beat it.. Oo... Tough luck, you cant.
you cant catch it anymore
you cant not that i knonk only on platinun
Im afraid you cant without cheats or hacks :( no legendary Pokemon is breedable.