Why is this a brilliant? I’m only 300 elo

I managed to checkmate by promotion for the first time and with a knight!!

Cool Mate in 9 that I found in game

First Brilliant move!

Why is this brilliant

What about it?

I took pawn with bishop

Nice little knight and pawn checkmate, I’ve not seen one like this before

Find the best move?!

Can someone explain this brilliant?

How does white win these type of positions? White to play, engine says +3 but I can't find any winning lines

Finally reach 700 elo lets goo

Is this a theoretical draw?