[22pajo]

Grunch

Preflop: Fold. A6s is not a raising hand from MP1 in this situation. It might be at a tight table with tight blinds but you have just sat down so i assume you dont know if both these conditions are true.
Flop: You have flopped the nut flush draw and an OESD which leaves you with 17 outs. However i believe we have to discount some of the OESD outs as yours is the bottom end of the draw. But i'm not sure how much we discount this for. (i might find out when i read the other replies to this post).
As for the action i believe a call is in order given BB's check/raise and getting 4.7:1 for a call.
Turn: As played call is fine.
River: Interesting. You have hit a straight and its been checked to you. Did you consider a bet for value?

In answering your questions i dont believe a preflop raise was ok, i dont 3-bet this flop and i dont raise this turn