I did this sick move against a opponent in one of my games try to find it.

Note: That he could of prevented checkmate although he could not do nothing about loosing his rook in this case here find checkmate you got to exploit what the defence gives you.

Nice.

Wasn't very hard to spot really. I'm surprised he didn't see it sooner tbqh. Good move though. :)

4. ... Re8 should be better because it would guarantee a mate sooner, I think (unless white blocks the e file with the knight or checks by Qxf7).

On the other hand, 4... b1=Q allows white to trade rooks, which would then let his king escape on Ke2, thus delaying mate.