Are fölött and felett interchangeable?
Yes, their meaning is the same.
I would prefer the ö-version especially for the case of "fölé" (above there) because there is another post position "felé" meaning "into the direction".
yes, but if you can, please use fölött as Hungarian is already full of e sounds.
Teacher with superpower!!!
the sentence is just hilarious :D
Is it super wrong to repül.after óvónő?
No, that's fine. You just shift the focus with that from where she flies to who is flying.
Nekem tetszik, a humor és "legutolsó" sorban a NYELVTAN a lényeg!
fent is not allowed in place of fölött?
No, fent is an adverb, which you can't use to refer to a noun. It's just "above" or "upstairs", but not "above something".