option A option B gives you more power, but that doesn't mean **** at all if you injure your hand and end up losing the fight because of it. Bad hand can also put you out of training. I'll protect my hands and fight on at the expense of some power.
Could never quite master that last turning it over bit...at least not when you are actually sparring someone..I actually lost power when attempting it. I just did what was comfortable to me...I never got to that level where my trainers would critique my punching technique that closely.
Preference. I feel a better skeletal alignment (and thus more power) when thrown palm down. Palm down also makes it easier to cut the opponent if the punch grazes
Yea, you can fracture the outer knuckles, the "bar-room" fracture is a colloquial term for it since those usually come from a hook, whereas a "boxer's fracture" is on the index/middle and usually originates from a straight punch good handwrapping will distribute the forces across the knuckles more evenly but you can also reduce the risk by landing more evenly
Palm down is better crisper and more powerful when done right however it is a lot harder doing it palm down and takes time to master the other way is a lot easier thumb up that is