I'll mostly avoid spoiling. After getting X at the Gate, one might have reason to backtrack. However, the game consistently crashes (at a black screen) when loading FG1 in either of the ways to get back there. Could you get around this with a teleport, maybe? (I would have to start over of course.) If I'm not mistaken, from what I've heard, let's just say, to avoid spoilers, you're really not supposed to.
EDIT: I can't seem to get into the fairy realm either. It doesn't crash, I just can't take the last step to get in, like there's a wall there.