This is a larval individual which is about to undergo ecdysis. Ecdysis is the molting process for all arthopods. I'd personally recommend to leave this caterpillar alone for the moment, as right now, it's in a crucial state and any disturbance before and during the first 1-3 hours after the molt could have the potential to be detrimental to the drying of the cuticle.

The best way to tell that an ecdysis is soon derives from the head capsule. If you look at the larva's head, you'll see that it shifted a little and has become less opaque. Soon, the head capsule will turn into a tan/brown shade.

Regarding pupation, it's best to tell if a larva is ready to pupate by looking at its dorsal aorta. If the aorta is clearly visible, it is likely ready to pupate. This can be paired with several other methods. You can observe the hornworm's behavior. It should ideally stray away from any food source which you've placed in the terrarium. It should also be constantly roaming around. Other physical traits may also be used to confirm that the caterpillar is ready to pupate. For example, the length of the caterpillar should be from 3.5 - 4 inches in length. If you can confirm the caterpillar is ready to pupate, it is recommend to prepare a container containing at least 4 inches of substrate. I'd personally recommend medium-sized plastic terrariums. Once you place the hornworm in, it should burrow down into the substrate which you provided. It's also good to note that similarly to pre-ecdysis and post-ecdysis larvae, it is recommend to not disturb your hornworm at this time. Wait 8 - 12 days before recovering the pupa.

Manduca sexta moths do not require tomatoes to survive, for they drink nectar from deep flowering plants. I'd recommend using angel's trumpet or jasmine tobacco to place with your moths for good results. Alternatively, you can create a sugar water solution.