Sergash: Missed opportunities:
14...Qa5! with the idea 15.Qc1 e5 But it is understandable to want to trade pieces when one is up by a full piece!
15...f6?! There was 15...e5! immediately, thinking that if 16.c4?! exd4! 17.cxd5 dxe3 and if now 18.dxc6? exf2+ 19.Kxf2 Bd4+! etc.
21.Bf2?! (21.Rc1) Re8. Why not 21...Rxc4. Capturing this free pawn was perfectly sound and the move to play.
Again on the next move 22...Rxc4 was the best move to play. Maybe Magnus played 22...f5 because after 22...Rxc4 he possibly did not like 23.Be6 but after 23...Nc5! 24.Bxc5 Rxc5 Black has no problem.
Another free pawn on 23...Rxf4. Magnus was not particularly materialistic at that age!
26...Nd3! instead of 26...Rd3.
33...Qg5+! first and then Bxd5, as per the program Komodo 9.2.
The simple 34...e6, as 34...Bc6?! was oppening a small opportunity for White in 35.Qd8+ Kf7 (35...Bf8 36.Bg3 Qf3! 37.Qd1 Qc3! 38.Qe2 (not 38.Bxc7? Qxh3 as the White king would be too exposed for his own good!) Bg7 etc.) 36.Be3 (threat: Re1-f1) Qe5 37.Qd2 Bf6 )
37.Bf4? White had only 2 "playable" moves here: 37.Bg2 Qxg2+ 38.Qxg2 Bxg2 39.Kxg2, or 37.Qg2 Qxg2+ 38.Bxg2 Bxg2 that transposes in the other move's line. After 37.Bf4?, White could call a mate in 10 moves, starting with 37...Bd4+ 38.Re3 Qh1+ 39.Kf2 Ne4+ 40.Qxe4 Qxe4 etc. with a mate after 6 more moves.