The b5-pawn is unsafe.

White has much better attacking chanses here. One of the reasons is that white has a much better center!

Good move, you that the pawn on b5 was unsafe and traded it off.

Yes.

Nxa4 or Rxa4 is better. But maybe white is hoping black moves his f6 knight so White can checkmate on f7.

The a4-pawn was unsafe, but it's still unsafe here, so 12...a3 just wastes a tempo. Better was 12.0-0

No, reachforgoals does not have a passed pawn. A passed pawn is a pawn that has no pawns between it and the promotion square on that file and on the adjacent files. Here, black's a5-pawn is not a passed pawn because of white's b2-pawn on the adjacent file. Passed pawns can be stopped at no cost at all in many positions if the blockading side plays correctly.

13...O-O 14. h3 would have been equal.

Agree with cplusplus. Its NOT an advanced pawn because of the b-pawn.

?? 14...O-O 15. Bc1 was much better, only giving White a very slight advantage.

No, black can block with 15...Bc8.

15. Bxf6 O-O 16. Bxg7 is the easiest way to victory.

You should have blocked with 15...Bc8. Now white has a forced mate.

15...Rb8 was best. After 16. Rxb8 Qxb8 17. Bxf6 Bxf6 18. Nxd7 Kxd7, White only has a slight advantage.

Black could have saved it with Rb8. I dont like 15 ...Bc8 because it will run into Nc6 and black has a problem.

16...Rb8 17. Qxb8+ Bc8 18. Qxc8# lasts 1 move longer. jkarp, just for testing purposes, I just linked you but did you get notified?

Make sure your pieces are safe, and check your opponent's previous move to see if you can win material by force. The most important thing is chess is safety.