This is a different kind of puzzle than you normally see on Susan's site, though the idea is an old one in chess compositions. The goal here is to find white's moves that force black to mate in 3. Some people have difficulty understanding the concept, but it is good exercise for your brain. Basically, white uses checks that black must respond to, the end result of which is that white is mated by black by the forced reply.
Crocodile, no even after 1. ..Re5, white can still force self-mate in 3, but the second move isn't 2.Ng3- it is another check at move 2.
After 1.Nf8 Te5! 2. Ng3+ Kf4+!! ..... there is no mate in 3 moves
Interesting that now it looks easy kk
1.Nf8! any move