if someone could explain it to me, i haven't played since 0.97 so if its been fixed since then, then please tell me, but during the MCs second evolution, he talks about all his power being focused on his spine and he should protect that, but during the arc when you're trapped in the prison and have to decapitate yourself to escape, it doesn't make sense to me that you are 'leaving behind' your spine, and he mentions that when he was bisected by the pink haired bastard (i forgot his name) he mentions how he grew back from torso down, not legs up, that shouldn't matter since his power is focused on his spine, so when you have to decapitate yourself, wouldn't it make more sense to cut below the collar to grow back from your torso instead of your head?
Well, the second evolution is basically to stablish the bases of Superhuman's powers, and balancing said power. Maybe the Mc's powers weren't fully developed and his regen was prioritizing the most important parts of his body.
So when he evolved, his regen gained a boost and now is capable of regenerating from his spine, meaning that having his head blown off wouldn't kill him anymore.
It's like Danica and Valravn, in a Dead end Danica would split him and the Mc dies instantly, but when he evolved and fought Valravn, he was cutted and split a bunch of times at the same time, worst than Danica's attack, and survived, even seemingly still conscious and ready to fight back instantly.
that's fair, however, another way to look at it, in the self decapitation scene, mc stretches neck so that can also be seen as stretching spine. there is also the fact that we learn later on, mc is weird when it comes to super humans, for the sake of not saying spoilers, all im gonna say is that that might have something to do with it
He decapitated himself on his first evolution and he achieved the clarity during his second an hour or so later. during the clarity he learns his power runs along his spine but is concentrated at the top and tailbone hence he will regenerate from the spine or one of those points (which is why the tails act subconsciously and any electricity triggering his nervous system leads to rapid uncontrollable growths). considering he was on his first it would have been easier for his body to regenerate from the head instead of messing with the brain. also how the person thinks their powers work will affect their development (such as Ella saying jakes powers were more people focused and limited than they should be.) TLDR his body saw it easier to regenerate head down.