First question I have is can you remove a mask once you have equipped it? I ask because I equipped the shark mask before reading my challenges and see that one of my challenges is to kill zombies while drowning without ABA. It does not seem to work when wearing the masks and I do not want to hack the challenge board due to already completing two of the 3 challenges. This brings me to my other question. If you have already completed a challenge then hack the challenge board does it keep the already completed challenges or does it erase them and give three new ones? Any guidance would be greatly appreciated!