weaken it and put it to sleep
you can, the catch is fairly easy even without a masterball although I woul use ultra balls if you arent going to use a masterball. I you knock out reshiram without sAVing before hand you can try again after the credits at dragonspiral tower
cave of oregan in sootopus
An ultra ball
Yes, you don't need a masterball to catch him. I've caught him countless times with an Ultra Ball. Just make sure you have over 100 Ultra Balls before challenging him, he is very, very, very hard to catch with Ultra Balls, but it is completely possible.
A fleeing legendary pokemon
try using dusk balls
The Master Ball is the strongest Pokeball as it guarantees a catch without fail when used on a wild Pokemon.
catch it, trde it, or use action replay depending on Pokemon game
No.
Use something like mean look to keep it from running, then catch it like you normally catch a legendary.
Use a quick ball and hope- but if it doesn't work it will flee