Apparently when Goku received energy donations from the other Saiyans he was brought to "full power" of a SSJ4, and when they charged him with more energy in the Dragons arc he was brought above full power, which he deemed "Super Full Power Saiyan 4." The latter power up would obviously far...
Because it didn't injure him enough that his Ki dropped past the point where his body could regenerate, nor did it destroy his core which can seemingly regenerate even if the rest of him is destroyed. It still took half his upper body off, which those generic blasts Goku shot at him during their...
the fact that it's got a senile old man and a shitty fanfic writer at its helm, and the company that animates it shits out bad episodes 7 out of 10 times