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.

26.0-0-0 looks like the normal follow-up. After 26…Nxg5 27.hxg5 Black is practically forced to play 27…Nh7, leaving White with a clear plus. Now the game becomes tense again, until Black overlooks an immediately decisive blow.

Black resigned.

Yes, the pawn can be taken en passant. Which is practically forced, as Black is threatening to capture on h3. A bishop sac on g2 is also looming. 22…Kd8 23.Qe3 is less clear (23.Qxf7? Rxh3).