> Ask about those round things in the wall next to him?

“These things on the wall are five very functional buttons, but I’ve only pressed the one in the middle so far.”

> Examine that upside-down flower/light/water sprinkler thing above Tom.

It’s some sort of switch that can be pulled, but it looks like it’s out of reach.

> Use CAN-OPENER to cut through fence.

The grate is thin, but given that it’s a cell the metal is clearly very strong and unlike the barrel, it’s not worn. The CAN-OPENER would have no chance against it.

Grab treasure, then dump aquarium on Tom.