I heard it from somewhere that if anyone ever loose the memory of first weilding the Keyblade you will loose the ability to weild the Keyblade forever is that true?

Where did you hear it? o-o

Um, I doubt it.

that means sora would lose the keyblade, wouldn't it? uz he lost it at C.O.

But he got his memories back after he woke up b/c Namine fix his memories. Plus while he was sleeping, Roxas and Xion had the keyblade. So maybe his memories were lost and that's why Roxas and Xion had the Keyblade ??:

You say you heard it from somewhere...

which means it could just be a rumor or someone read it off a fanfiction and not true at all.