Tactic #3, Difficulty: Easy, Black to move.
Solutions:
#1: 1. ...Ng4!! 2. Qxg4 Qf1#. The only way to continue the game would have been 2. Qg1, but then 2. ...Qxc2 and white is lost in any case.
#2: 1. Rxh5! Re8 (1. ...gxh5 2. Nxh5 Qxe2+ 3. Kg3 and black can't stop mate) 2. Qxh7+ Kf8 with a strong initiative and material advantage.
#3: 1. ...gxh2! (not 1. ...hxg5 2. hxg3 and white stands better since the knight cannot move due to Rf8+ winning the rook.) White cannot stop the pawn from queening without giving up the rook for it, so white resigned.