i know that you can fight him on route 6 only three times in the grass patch closes to the underground path using a max repel after that i don't know
You can't.
you have to beat elite 4 then catch all unowns.
you have to start with Bulbasaur.then beat the elite 4.after that Raiku will become then you have to look for it
you dont
catch it in the wild
catch pikachu in viridian forest and then use a thunderstone on it. same for firered and leaf green. ( kkrenzke says- ) they mean the legenday electric dog pokemon, your thinking of Raichu the evolved form of pickachu.
if you have firered or leafgreenyou will be able to catch entei ,raikou, suicune only if you beat the elite four then when you catch the three lengendaries then migrate then into Pokemon diamond
To get Pokemon firered on PC download a vba and Pokemon firered ROM
You can catch a Ho-Oh at Navel Rock in Pokemon FireRed.
You can catch Moltres at Mt. Ember Peak in FireRed.
articuno, moltres, zaptos, mew, mewto, suicine, entie, raiku
you can not catch him