try using dusk balls
with a ultraball
Yeah it is possible to catch kyogre with out wasting your masterball you wont have to use it until you see latias and latias requires you to use your masterball.
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
A fleeing legendary pokemon
Sorry but you have to catch Regice, Registeel and Regirock in order to catch Regigigas.
No.
Use something like mean look to keep it from running, then catch it like you normally catch a legendary.
you cant. regice regirock and registeel are all part of the hoen pokedex
Sorry dude, you can't get registeel in platinum without a cheat. But you can catch Regigigas in Platinum, but you'll need all three of the Regis to get him.
Use a quick ball and hope- but if it doesn't work it will flee
Kyogre and regirock-regice-registeel
the masterball is for any Pokemon you want, it can catch them without fail ( it will ALLWAYS work ) . you are supposed to use it for mewtwo though. :P