We should mostly check river with A4s on Q94Q; the shove is too ambitious and runs into a lot of full houses.
Flop Qc 9d 4d, pot ≈10.5BB, SPR ≈3.5. We have bottom pair with a weak kicker plus the Ac, which gives us a backdoor nut flush draw. Solver prefers a small c-bet or a check; our 3.6BB bet into 10.5BB is slightly larger than ideal but works as a small value/protection bet.
Turn 2c brings a second club and improves our hand to a flush draw plus a pair. Solver leans heavily toward checking here with this combo; betting would mostly get action from stronger made hands and flushes, while checking lets SB continue bluffing and protects our check range.
SB now bets 7.3BB into 18.1BB. We’re getting about 3.5:1 and need ~22% equity; with a pair and a flush draw, we have far more than that, so calling is mandatory. Raising is mostly unnecessary and would fold out hands we’re ahead of while getting called by stronger flushes and made hands.
River Qs pairs the queen. Our hand is now A4 with a queen kicker and a missed flush draw, so we effectively have a weak bluff-catcher. Solver wants us to check here almost always; jamming 25.2BB into 32.8BB is too ambitious and runs into full houses (QQ, 99, 44) and strong queens that call very often.
Note: Shoving river with A4s on Q94Q is overly optimistic; this combo should mostly check and occasionally bluff small, not commit stacks.