what i would do is save before you go into battle with it or either get an action replay to use cheats :)
you can't get him again.
you cannot catch wild rare Pokemon in xd but you can catch the trainers rare Pokemon, if they are "inpure"
if it faint's it dissapear:(
You Catch it.
you can catch sudowoodo and smeargle
you cant catch it it is rare
No once any Pokemon has fainted you can not capture it sorry
You catch them. Or trade for them.
It is rare on One Island
tropius is a rare pokemon. but you can catch him near the water institute.
No.
Rare Pokemon come randomly when you're in the grass or cave.