MCC Chess Puzzles
These puzzles are dumb... they are all trick puzzles that have easy win like checkmate in 2 or 3, but the trick is that there is actually checkmate in 1... dumb.
The last puzzle is wrong as white has 2 alternative moves besides the intended solution to mate in 2 moves. The position should be mirrored to enable black to castle if white tries anything funny. And don't forget to tick the black castling box!
Don't know what you are trying to do. Your last diagram still has 3 solutions as black cannot castle. Ask StockFish!
Btw, if you insist on doing this without castling rights, you should add a black bishop on b4 in your diagram. But I bet there was a black castling right in the original publication of this puzzle. It's probably a golden oldie!