Yes the possibilities of Photoshop are endless! As well as the ways you can apply different techniques.
But like any creative program it depends on the one who uses it or even on his mood.
The difficulty of the program is not in the use of the program but in editing a photo as it is needed
The photo must be edited without losing its balance.
This is why the most common mistake is to over process on the skin, so that the detail and the real texture of the skin ends up corrupted.
There are also techniques based on the knowledge of a makeup artist and a plastic surgeon.
One must understand the balance between shadows and light, but without interfering in the lighting of a photograph. You can also process the bones of a person's face, even his height, without altering his features, always working on improvements.
Surgeries have to be surgical, which is why they are difficult. That's why in the creative part, you need a clear mind and inspiration!