Is it possible to unclone stamp a picture. For example if you have a picture that has been cloned stamped over someone's face in the picture is there software that can unclone stamp it or predict and fill in the missing parts of the face?
It all depends on what you mean by 'picture'.
If you have a single layer JPEG then the answer is "No."
If you have a "raw" image with all of the editing steps appended to the file the answer is "Yes."
If you have a PSD (or similar file for an application other than Photoshop) the answer is "It depends." If the 'clone' was accomplished using layering, then if you PSD is still multiple layers the answer is "Yes." If your PSD has been flattened to a single layer the answer is "No."
There is software that can attempt to fill in missing parts of an image. Photoshop has a content aware fill mode, for example. But it's not intended to work out accurately what someone's face might be.
This might work with small parts of the face missing (e.g. if thin lines were over parts of the face - like tears in an old scanned photo sometimes produce).