"hypothetical" mate in 4

This is my first attempt at fen so I'll probably mess it up.



White to move and mate in 4.

EDIT: PM answers to me please
EDIT: I messed my fen. 😀

It won't let me edit once more, but I made another mistake on the position after I looked at it this morning. Its my first time with coming up with a puzzle so I was expecting some mistakes. 😕