O.K. I just beat the game but I heard that Revan was in this game somewhere and I could not enter the cave on Koriban because I was not all light or all dark, I think I may have skipper over a bunch of cool stuff by accident, what can I do???

you'll have to go back as a character with a more definite alignment, i guess. it's not THAT cool in there, i mean there's some alignment points to be gained and a few random items to grab, but that's it.

theres also an infinite exp glitche in there

That's true.

Plus, I think it's always cool to fight with your "former self"...

wait wait, im at the end of the game as dark side...and i dont ever remember fighting reven...

i remember i had to wait until i was more aligned dark in order to go into either a cave or a academy and fight that ugly dood

You have to be a prestige class before you can enter the secret cave. This is because once you reach that class, you're more "defined" on what path your character is going to be taking.