A9o vs 2 players

I would raise bigger on preflop like 1200, because if you raise to 900 then UTG has to call only 600 chips to fight for 1920 which isnt really much and also there is chance that BB can call (which actually happened).
Also it would be hard for me to call his allin on the flop because you have only top pair with not the best kicker and there is also 1 more player behind you who has to act and who called your raise and his stack is much bigger than UTG's.

I agree about preflop raising size.

BB in this situation does not represent anything good, I think any better hand than mine would raise both preflop and on flop. Going forward there is just too many scare cards for him to come on the turn versus 2 players, that he just needs to be raising, so I feel confident going all in vs UTG knowing that BB will fold.
UTG on the other hand has a good situation to squeeze, I bet the flop and BB calls, there is 6500 chips in the pot and he can push his hand with any ace, KQ, JT, QJ, some suited connectors. I think if I fold A9 in this situation then I just fold too much

I wonder do we call with this hand even blocking fl/dr with our 9 of hearts!? What simple is saying here?

I don’t think I would call this flop. I expect he’s shoving only with better hands and that you are in best case against a flush draw.

Cheers,
SDK1987