a) The exact same ending as the theatrical except when you get the final pan over Dakota's drawing you see a single head over the kid instead of two. That was called "Happy Ending" on the menu.

b) Instead of Famke rushing Dakota out to school, you get a shot of her tucking Dakota into bed. She gets up to leave, begins closing the door and Dakota asks her to leave it open. Famke says "you know I can't do that". As she closes the door you see it's one of those institutional doors with the little reinforced window on it. Famke walks down the psych hospital hallway talking to another doctor saying "I'll check back with her next week" or something along those lines. Switch to inside the room, Dakota does the hide & seek count-to-ten thing, gets up opens the closet and we see her blankly looking at herself in a mirror, then fade to credits.

The other two endings were similar to the second one with Famke saying something else to the doctor, like "I'll keep coming back everyday till she's better" and I don't think it cut back to Dakota going to the closet. This is the ending I preferred.