To question #1:
Everything I've read implicates the thalamus as the critical structure whose function is being disrupted when people lose consciousness due to trauma, seizure, disease.
Although the shape of the whole brain is distorted by the kind of impact a hard punch represents, it is specifically distortion of the thalamus which probably causes temporary unconsciousness.
However, the thalamus itself is regulated by the reticular formation of the brainstem:
So, trauma to one, the other, or both at once, could cause temporary unconsciousness.
Apropos: I can't recommend any activity that involves blows to the head: