Puzzle of the week #342

Level: 
2-Knight
Chess Diagram: 

[Event "Puzzle #342"][Date "2018.03.31"][Result "1-0"]1. e4 e5 2. Nf3 Nf6 3. Bc4 h6 4. Nxe5 d5 5. exd5 Nxd5 6. Qf3 Be6 7. O-O f6

This opening sample has reached a critical point after only 7 moves. Your tasks:
a) What has black done wrong?
b) Why is this a critical point?
c) White to move and take advantage of black's mistakes

Total available points for this puzzle is 15. The answers will be published next time together with puzzle #343.

Puzzle #341 solution:
Gadimbayli – Paramzina, Baku Open 2016. This week's best answers are by the top scorers:
a) It is the opening of the game because nobody has finished their development
b) White has developed 3 pieces and grabbed the center. Two strong knights are in the middle. One knight stops black queen to move out
c) Black's queen, king and king side bishop are all blocked. Queen has no square to escape

[Event "Puzzle #341"][Date "2018.03.25"][Result "1-0"][SetUp "1"][FEN "rnbqkb1r/3nppp1/pp1p3p/3N2B1/3NP3/6P1/PPP2P1P/R2QKB1R w KQkq - 0 1"]1. Ne6 fxe6 (1... hxg5 2. Nec7+ Qxc7 3. Nxc7+ Kd8 4. Nxa8) 2. Qh5+ g6 3. Qxg6#

Correct solutions:
Aiden, Mengbai, Joey, Coby, Zhengyu, Matthew, Eric, Lyvia - 20 points
Glyn - 18 points
Itamar, Lucas, Walter - 12 points
Blake - 11 points
Steven - 5 points
Chris - 1 point

FINAL STANDINGS:
Matthew - 210 points
Eric - 200 points
Lyvia - 188 points

Coby - 176 points
Joey - 172 points
Aiden - 166 points
Mengbai - 165 points
Glyn - 144 points
Zhengyu - 124 points
Walter - 115 points
Itamar - 109 points
Blake - 102 points
Lucas - 93 points
Jacey - 82 points
Brian - 80 points
Chris - 26 points
Darius - 20 points
Steven - 7 points

Comment: 

Opening