There is no Ng7+. I think you mean Nf7+.And anyway it's white to play and WIN. Kh4 makes it much easier for white to win as he has many possible moves that ensure him victory.

Instead of 4...Ng7+,try Kg4...makes it much harder for white to win...The check with the Knight is not forced..This is the key move which allows for the mate in 17.I saw this move befor i put it on my chess engine..turns out i was right!

I made this up by myself

No, but it should be. 5.Qh4# is a much faster mate than the puzzle's move sequence.

Its not Qh4#

Anybody tried to do it with an engine yet.

5.Qh4#