And now 12…a5 seems a valid try, pressing the b3-knight and vacating a6 for the bishop. Black is OK.

Yes! White just marches with the h-pawn to activate the h1-rook.

A) 11…Nxh5 12.Rxh5 gxh5 13.Ng5 f5 14.Ne6 Qe7 15.Nxf8 Qxf8 wins back material and leaves White slightly better;
B) 11…gxh5 12.Nh4; or 12.e3, yielding a big positional plus;
C) 11…Qe7 12.hxg6 fxg6!? 13.e3 ♗xf1 14.♔xf1 ♘bd7?! 15.♘g5, and White had the initiative in Wagner-Pavlovic, Berlin Wch rapid 2015.

White is clearly better, with the rook on h1 well-placed.

Undermining White’s stronghold on e5, opening up the diagonal for the dark-squared bishop, while the g-file may prove useful as well on occasion. What more do you want from one move?

Not the best reaction. 22.g3 would be better.

22…Bxf4! 23.Nxf4 gxf4 24.cxb6 Qc6 with 25…Qxb6+ to follow.

This is no longer a solid spot for the knight.

And here Nikolic failed to find the only defense against the threat 26…Rd4!: 26.Rxd8 Rxd8 27.Qh4.