$200 NLHE Full Ring: Live 1/3, 2pair on 4flush board

New player so sorry if these points seem obvious.

UTG, UTG+1, and HJ limp. I raise to $15 from the BB with As8s. UTG and HJ call.

Flop Ah8h4c. I bet $15. (In hindsight, too low). UTG and HJ call.

Turn 6h. I bet $35. UTG calls.

River 2h. Action? Effective stack about $200.

My thoughts —
-on flop, in hindsight my bet was too small. I was conflicted because I wanted to charge flush draws, but at the same time didn’t want to blow out worse aces. In hindsight a little bigger would have been better
-on turn, the flush gets there. However, I suspect that if I check he’ll bet nearly everything and I won’t know where I stand. I bet $35 with the intention (initially) to check/fold river if called.
-...however, when the fourth heart comes on the river, I rethink things. I decide to bet $55 with the intention to fold to a raise. I would expect at least some low flushes to fold to a bet on the four flush. I don’t expect UTG to have many Kh or Qh hands after limping. Further, if I were to check the river, he’d almost certainly bet and I’d fold. I’m betting $55 into a pot of about $165, so this needs to work about 1 time out of 4.

Any thoughts? Again, new player, so sorry if this seems straightforward.

In preflop your rise x5 from bb shows a lot of strength and on the side of UTG and HJ they may be players who speculate or can wear strong combinations but choose not to re-raise.
The flop bet should have been bigger, but not so big. Maybe 60% of the well would be fine, since you don't want to isolate yourself too much with hands like QKhh that will always pay you.
It is preferable to also include premium AK; AQ; KK; QQ; .. who will not hesitate to pay.
On the turn I think the check-raise x3.5 or x4.5 would work to rule out all the lanterns that are bothering.
Your hand is good enough to let it run worthless.
If you prefer to continue betting on the turn, it should be a size around 1/2 and 2/3 of the well, to achieve the same effect (remove Ax lanterns; etc)
You make this decision, taking into account your battery, the type of villains you face, etc.
But one way to better specify the rank of villains is to redouble their bet. And if it makes us a 3bet, we would be in a very fine line between the call / fold. But at this point I would be more inclined to fold.
On the river, I think the check is a standard move. You have tried to remove the villain but if it remained until this point clearly our rank is being surpassed by better lines.
Grettings.

I like the river bet/fold. You do get some Ax hands that got there on the river to fold. Obviously higher flushes will call you but they can have like A5 with the 5h that might fold.

You write: "I suspect that if I check he’ll bet nearly everything and I won’t know where I stand".

This is not the way you should think about poker. You should bet either for value or bluff not for information. The info part can be a bonus but not the main reason to bet.

Also if a player bets nearly everything when you check you should check a lot of your made hand and let him bluff (and you often call).

Flop: You have top 2, which is most lilkely the best hand here. You are facing multiple callers with a flush draw on the board, so bet out quite large. I don't think a pot sized bet is too crazy here.

Turn: As played, you bet around 1/3 pot. You seem really weak here, especially in combination with the flop bet. I'd bet around 1/2 pot. You are getting value from worse aces here.

I think checking the river is ok. Not many people would bluff there, especially with your small bets throughout.

I love isolating limpers, but 3 limpers and from the blinds with A8s is a bit iffy. You are going to be out of position postflop, and your hand dont play all that well, although it does help, that it is suited. But even so I would probably just knock my option and try to smash a flop, like you actually did.

Also if you are going to raise, it need to be far larger than just 5BB into 3 limpers. Everyone is going to call that, so a raise of this size really does nothing other than bloat the pot, when you are out of position with a not all that great hand. If you make it 30$ here or even 40$, now maybe you can generate some folds, but I would probably prefer to use another hand than exactly A8s, if I need to make it this large to get folds.

Your flop bet is to small, and when you get called in both spots and see this turn, its already time to slow down and check-call. And of course you are pretty happy, if it gets checked around, and you see a non heart river. That did not happen though, and this kind of river is actually fairly interesting, because normally you would prefer to bluff with blockers.

But its not possible to block the flush without having it, so what hands do we even pick here to bluff with? Paired hands are the obvious candidates, but I would probably prefer to use something weaker than this hand. Its almost to good (still) to turn into a bluff, because if Villain check behind, and this will happen sometimes, you are probably good at showdown.

The preflop raise is a bit small for three limpers but not that far off. Really depends on the game you're playing in. Some sites are full of limp-calling stations who you need to bet substantially higher to get folds. The general rule of thumb is your raise size + 1BB for every limper. In this case 18BB would be a standard raise but given your position and hand strength (lack of play-ability) you want your fold equity to be slightly higher so a 20+BB raise would likely be ideal. Again though, you're preflop raise wasn't too bad, though generally against weaker limp-calling stations we want to play much tighter and raise premium hands.

The flop bet is not horrendous but definitely too small. You want to make people pay to see draws when you have this hand (especially in a multiway).

On the turn against three players, it's time to go for a check-call/check-raise. If you get a bet and a fold before it comes back to you, it would be a good spot for a check-raise. Your hand has very good showdown value and again you make your opponents pay to see another card. Put the pressure on your opponent here. Then on the river your raise might get you a cheap showdown to many hands other then the nuts. Check-calling is standard with three players still in the hand, and giving it up on the river when the fourth heart comes to another large bet is perfectly fine with that texture.