I might have played the a8-rook first, but this pawn move seems to be called for pretty soon anyhow.

Rab8 (threatening bxf, Qxf (or the B b2 is lost), and then Ne5). Or Ra-g8. Or Re8. Or Nc5. Black has a lot of moves here. I'm not sure I would have committed myself to this, being able to keep both bishop closed in their aims near to my king. White can't attack f5 with another piece easily enought for me to worrk. Am I right?

To make something less effective or to weaken.

Undermine means that now black can't affor fxe, fxe,Bxe4+, hiw pawn chain will be destroyed. So he has to do something about that. Black now would have to play e3, in order to leave f5 well guarded, or exf, allowing the Q's exchange (not good nor bad). In both cases, black's recently created chain is destroyed. That was the questionable part of black's previous move. But you can't say that the destroyed chain is not good for black, if it attacks heavily into white's field.

Is ...e3 not playable?

Yes, maybe that is better.

The only problem with f5 is that after an exchange at g7, it will remain undefended. So this is the main black's weakness. White has lost the chance to threat h4, so the column and the subsequent threat on g7 is doomed. But after the exchange...

Rather odd-looking position: especially the placing of White's bishop pair, and Black's knights.

I would have preferred ...f4, but that doesn't seem to be playable here.

f4, e5+ and black will be in very big troubles: where if kg8, h4, and if Kg7 or Kh8, e6+

Now e3 can't be played anymore.

A most interesting duel for the control of the center! Wonderful game!

Pieces seem to find a place to hold, despite all. And black has two not-playing knights ready to activate...

Temporizing?

This is to prevent b4 in case of Nc5...

I thought if Black tried 31. or 32.Rf4, White play this same rook advance.

A well-placed knight. He'll be very hard to shift from there.