Do finger prints survive fires??

They can and often do survive in several ways. Heat softens the skin secretions in fingerprints. They take up soot more easily. When they cool, the secretions harden, and often all that's required is to brush away the excess soot. I've had fingerprints etched into an aluminum can by the action of heat on the slightly acidic skin secretions. I have even seen cases where the differences in how heat charred paper to leave fingerprint ridges clearly raised on paper that was completely charred and so fragile that is was very hard to preserve. None of this means it's easy to find them or that they will be present in even a majority of cases.