I don't know of any classical examples of reversed petrification following damage to the statue... it has probably happened a thousand times in DND campaigns... he he he... when I was much younger, and thus fascinated with such things as the following, I remember casting stone to flesh on a mountain side, turning it into a giant butt and killing a red dragon when the butt farted into its fire breath and exploded everything. Somehow the party was unharmed, though perhaps traumatized. Practically flesh-to-stone might be used to hack through a stone wall or something, or to make an edible flesh basin in a floor (but would it be cannibalism? i.e. Is the wall turned into human flesh?)...
Only 4 more simple functions, and creatures will be fully exposed to temperature effects (melting, becoming gas, blistering, frost bite). A little bit more work to get items and then a little more to get all of the landscape features. Then temperature is done. Right now, creature body parts have temperatures, but they don't suffer any effects.
You'll do heat exchange with the air, the ground, and your inventory, as well as anything that hits you. I guess when wrestling is added, you'll do heat exchange on a part-by-part basis with your opponent. You should be able to boil blood, although I haven't quite figured out how to differentiate blood temperature from body part temperature. I guess heat exchange between your body parts should be faster if you have a circulatory system.
A simple example to overlook would just be holding an ice cube. In a few days of programming, it will melt in your hand, and make your hand colder, until your hand heats itself up again. If you keep doing this with many ice cubes in succession (keeping your hand at a low temperature), you'll get frostbite on your palm. You'll also get blisters or burns if you try to cool off hot rocks by holding them. Weapon heating spells will hopefully all work naturally with no extra coding required. Lots of things should work naturally... perhaps now I'll start reaping some of the rewards of all this basic structure.