Miracle

[paulpablo]

If in some unfortunate accident a person is caught by the fire then which part of the body you think get exposed to the fire first. SKIN. Until fire find its way to internal organs, the unfortunate person might not be living anymore.

Yes the fire will burn the skin first, but skin is very very thin, a human being suffers heat stroke and other heat related deaths just by being in a hot room sometimes, if you throw them in a fire and ONLY replace their thin layer of skin to protect them it will do nothing to stop the heat reaching the brain, the veins and so on and so on.  Another way to look at it is if you walk into an oven and you have invincible skin that heals at a supernatural rate, this doesn't mean the rest of you will be invincible, your blood will boil your brain will dehydrate you will have some sort of heat stroke.  The heat conducting through the air will be enough to kill you.
It just simply won't work.
If you're abiding by the rules of biology and want to keep someone alive and in pain, throwing them in a fire and only replacing their skins won't work. Their brain will shut down from death and the pain receptors will be sending messages to non functional brain.