I don't know if any of the species in the pic are food for desert tortoises, but they like Prickly pear a lot, is what they eat in the wild. I just buy some pads at the super market and thrown them in the floor. Some times I just cut some pads from my prickly pear tree and do the same thing.
I don't know the time to recover from a stone removal procedure, but I can guess he's still under pain. Maybe give him a few weeks to fully recovery and see if improves. But yeah, the vet could check him out again to see if everything is fine with the operation he had.
I know, my mom has a lot of roses plants and they are flourishing. A neighbor has an hibiscus tree too, and he gave me the flowers after the flower start to decay, so my Texas DT can eat it.
When I was little, we had a Texas tortoise, and me as a child not knowing a lot of tortoises, I pick him up and "flying" him. So much fun for me, but I believe not for our tortoise.
Today here in North Mexico near to Texas is like 15 Celsius, so I guess my torts won't awake today or tomorrow. But next week we are going to have low 30 celsius weather, so I believe they would awake, but we never know.