In the following game, White was in a position to create an Octopus by move 11, which he went on to create on move 15. My question are after the game score.

Melkumyan - Postny 2012
1. d4 d5 2. c4 dc4 3. Nf3 Nf6 4. e3 e6 5. Bc4 a6 6. Bb3 b5 7. a4 b4 8. 0-0 Bb7 9. Nbd2 c5 10. e4 Nc6 11. e5 Nd5 12. dc5 Bc5 13. Ne4 Be7 14. Bg5 0-0 15. Nd6

Questions:
1) What mistakes did Black commit to allow the Octopus to be created on d6?
2) Why can't he win the e4 pawn on move 10?