Halo2-halo2-halo2-halo2-halo2
yes
the primary ones are: iron skull, black eye skull, tough luck skull, catch skull, cloud skull, famine skull, thunderstorm skull, tilt skull, mythic skull and the secondary ones are: blind skull, cowbell skull, gruntbirthday party skull, iwhbyd skull and all of them are accessible from the start so you dont have to look for them. hope i helped :P
Enemies are higher Rank,for example there will be more brute captains and ultra elites etc.
not very
No.
because skull protects it, skull is a hard bone to protect our sensitive parts like, brain, face.
Well a tiger skull is pretty hard.
really really hard
VERY
because it is hard.
skull or cranium