So he was the one that received electroshock? The other kid died?

Since he was Nicola (Nicola was a part of him in his head) he was the one that received electroshock when little, right?
The kid that was trying to jump that got hurt... really died? or he imagined that?

I really liked this film, but it confused me, since some parts you don't know if it was all inside his mind or something else.

Thanks in advance.