Why is taking the knight with queen the best move?

Mate at the edge of the board i did today.

A Brilliant move?

What about it?

This is my first brilliant move. I’ve played casually for a while but only recently started really getting into chess. I’m confused as to why a long castle would warrant a brilliant?

Why can’t I en passant in this position?

What about it?

Chess.com won’t let me en passant in this position. Am I missing something?

What can black do to defend?

What about it?

As above, I assume there’s a good move here for black but I didn’t see it, I played pawn to e5

[WHITE TO MOVE] Mate in 4

I’m so confused

What about it?

Isn’t rook f8 check in 2 or am I crazy

Wasn't looking at time, probably for the best...

In a game it said this was a blunder, in this line why would I not take the knight here

Why is Qd5 the best move and not Qg1?

Proud of finding this in one of my rapid games.

What about it?

Before Nb4, Black had a slight advantage, but this move is a blunder.