Pictorial progression on the life of a green tree python.

Most green tree pythons won't exceed 6', and stay slender at that.

As for the frozen prey, almost all captive snakes that are acclimated to captivity, will take take dead prey, either frozen/thawed or freshly killed. Sometimes you have to do the "zombie rat dance", wiggling it a bit. Some babies will only take live for a few times, etc. Most generally still constrict the prey, though some will just take it and swallow it. I gnerally warm it up to body temp in a ziplock bag in hot water.