Premature, but Black does have to be careful to meet it correctly. The problem for White is that if Black does meet it correctly, White is likely to fall behind.

Black hasn't thought this through. Wishing to counter-attack, possibly concerned about f7, Black overlooks the immediate threat to the pawn at e5. Probably the best method of defence is 2....Nc6 (Developing a piece and protecting the e-pawn) 3.Bc4 ... (Definitely threatening an immediate checkmate by Qf7#) 3...g6 (Blocking the mate and attacking the Queen) 4.Qf3 ... (Renewing the Mate threat from a different angle) 4...Nf3 (Blocking and developing) 5.Qb3 ... (Still attacking f7, though no mate threatened this time) 5...Qe7 (Protecting f7). In the following moves, Black can play ...Bg7 and ...0-0 with a fine game.

Consider all checks, captures, and threats that your opponent could play. Qxe5+ is both a check and a capture.

Preferable seems 3...Qe7 4.Qxh8 Qxe4ch, but the loss of the rook still spells disaster for Black.

It was worth the time to pick up the rook!

There was but one sensible move here: 4...Kf1. The h-pawn still falls, though, and the Queen escapes.

Consider all checks, captures, and threats that your opponent could play. Qxg8 is a capture.

Black is now the material equivalent of a Queen down, and quite lost. Can he recover?

6...Qxe4ch was a goodish move.

Not too bad, even though it allows Black's next move.

This would have lost time had Black now played 10...Qe5ch 11.Nd4-e2.

It's good that you know this is a bad move. The question is: how can you prevent such moves in the future? The two ways are: 1. Slow down. Think for at least 2 minutes per move. 2. Consider all checks, captures, and threats.