Question about Legendaries

[Illzor]

For pokemon who you can befriend on the first try, such as mew, celebi, regis,jirachi, etc...can u beat theam and return to befriend them later?

 

[top8inU.S.A.]

You can only befriend Celebi and Latias the first time and yes you can return.

 

[Jason]

you alwyays can return later