Kingdom Hearts PSP x PS2

umm i wanna if the psp version is the same as ps2?ive finished kingdom hearts 1 and 2 in ps2,the main protagonist is sora in kh1 and sora's nobody 'roxas' in kh2,so can any1 help me?

If you are talking about Kingdome hearts Birth by sleep which im assuming you are because thats the only KH game for the PSP then its a whole new story different from 1 and 2.