Would pressure applied to someone's skull by hand, be capable of changing the skull shape, if applied hard or long enough?

Unlikely: Not usually - once the skull has solidified after the first few months of life it is relatively fixed. Pressure before the fontanelles close can cause changes but it would need to be sustained for weeks to months.

Yes/child, no/adult: Artificial cranial deformation is a form of body alteration that some american and african tribes used to practice. It was achieved by applying constant force to children's skull. Check it out on wikipedia. Unlikely to change an adult's skull shape though. Skull bones very tough by then.

Unlikely in an adult: This is unlikely in someone who is 22 years old. The bone and skull at this point is fully formed and solid. The sutures of the skull are fused and solid. It is unlikely that hand pressure would change the shape.