If I put on bandana skull and play through campaign on legendary.....
 

Can I still get achieves for beating game on legendary? Even thought bandana gives me infinite ammo

im pretty sure you can

Indeed you can.

Yeah they still unlock, this skull made this game rather easy for the most part.

Not "easy" but "doable" for rookies like me.

-Greetings.

Partially not true. It is doable and with that skull and the boom skull game is a piece of cake. Though the Library Level is annoying with boom skull on.

You can turn on as many skulls as you like and it will not affect the achievements.