AJ Riverdecision

I think calling or folding the river is both fine. While he could play some missed draws this way, I don't think he's bluffing on an AK board and usually that's some sort of 2p or backdoor flush draw that hit the river.

Cgf

What about check behind turn line, what are we betting against here?

i think betting turn is good, especially at micro levels.

we get value from worse Ax hands, some Kx hands, gutshot +diamond, Kxdd etc.

if we are check raised then it is most often 2 pair+ and we can safely fold

without any information on villian i would probably fold the riverbet.

What hands does he faltcall a UTG raise with? He playes the flop OOP so i think he does it more with weaker suited Aces and some suited broadway connector aswell as mid/low pp. If hes a bad player there are probably a lot of Ax and Kx hands in his range too. Do you know if he playes fit or fold OOP with drawing hands? Would be a very valuable information.

OTF i asume he at least hit in some way so it could be Kx Ax 66 and maybe he called draw like QJ or JT.

OTT he could continue a flush draw. We at least have the nutflush draw blocker so we could assume he didnt call the flop with Axs. its now more likely he has broadway connectors and he picked up another possible set.
I would bet more here, maybe 3/4 pot to see where i stand and if the turn makes the flush we at least made villian make a -EV decision.

OTR there are quite some hands that have us beat that make sense with the line he took.
He could have: KJdd, QJdd, JTdd, A6, A9, A7, 66, 99, 77.
Without more detailed information on villian i assume we are beat when i get called on flop and turn to be raised for 2/3 pot on river with quit a lot of his pf call range beating us.

I dont think he bluffs in this spot vs an UTG raise with an AKx flop.
Only semi bluff i could imagine would be Ax hands but this would need more information on villian and more complex thinking on his side (not very likely at micros). He would need to see weakness in your low turn Cbet and think you are semibluffing here with a PP like JJ, TT or QQ that his A high hand has beat. Also this would require him having some stats on you to know that you are agressive on flop and turn to much while folding to a lot of river raises.

Tob

I wouldn't check back the turn. I think he's calling worse Kx and worse Ax and possibly even gutshot and backdoor flush.