Battery Advice, please.

Hi! First, let me say that I’m not very knowledgeable on stuff like this, so please be kind. Can I charge a 3000 mAh 20A and a 3500 mAh 10A battery at the same time on a 2-deck charger since they’re both 3.7V? Also, on another battery, the wrapping has peeled off just a little bit on one end. Is it still ok to use? Thank you in advance!