By moving, the pawn has 'discovered' the check from the queen. Useful notion. All the same, I think 51...Qg3 was still best. White has no hope whatever of a stalemate.

It's discovered since you didn't do a direct check. But, the pawn stopped a check, and once is moved, the Queen attacked. Yes, it's discovered because it's a sudden check that was, more or less, discovered by unvailing the Queen.

52...Qg3 or 52...Qf4.

I like this move almost as well since Erika's threatening to promote the pawn. The only thing to be weary of is a stalemate which you don't want to allow with a won position.

?? Letting you win the last piece. Having said that, you don't need a promotion to checkmate.

More accurate, Qg2, keeping the W King on the h-file, with no escape. THEN promote the pawn (or play ...Kf7).

I was going to say that 56...Qg2 was best. And, you don't even need to promote. Not only that, but you can and ought to ignore the f pawn. Instead, after 56...Qg2 the King's confined to one corner as the only moves are 57.Kh4 or 57.Kh6, and then, best is 57...Rd7 which forces 58.Kh5, and then, 58...Rh7# is checkmate since there's no way out which would result in this final position.

Much, much better was 57...Qg2.

Agreed, and that's due to what I noted above. Important to note that it would've done the same thing.

Having brought the pawn all the way down to f2, why not move it once more and promote it? You don't have to give 'check' every move. You want to give check only if it leads you closer to your goal. 58.f1=Q would have led to checkmate in two more moves.

Well played - ready to escape into mid-board, and make Black's job harder. It is still mate in 3, but midboard checkmates are less easy to figure out for the inexperienced.

It's mate in 1. Can you find it, Erika?

Understandable, and a good way to protect the rook. But 60...Qf6 checkmate would have ended the game right here.

ION's correct, and unlike before, I would've seen this mate.