on the manga vexen data kill xaldin and on kh2 sora kill xaldin what of them is the right one ????

Easy. Sora killed him. What happens in the video game is right.

then why they r doing things like this I mean doing things didnt show on the game ???

It's just a manga. It's not persae a definite part of the storyline, but certain things fit in with the time (there could very well be Vexen Replicas).

it's just manga, there are different parts in the manga then in the actual video game

here were you can find all the differences

http://kingdomhearts.wikia.com/wiki/Kingdom_Hearts_II_(manga)

thanks guys

Basically the manga tries to tell the story in a funny way, so a lot of things turn out to be fake. So, the game's are always the way things happened. Listen to the games before the manga.