Every Week
once a month at least
Gerbil hair loss may be caused by many reasons. The gerbil's cage mate could be fighting him for dominance, and could've bitten there; you may have to watch them. Mites can cause hair loss, and that needs to be checked out immediately. Or the gerbil is simply bored and is over-grooming. Throw in an extra toy or something new!
You should fill it's bowl just to cover the bottom but if your gerbil needs more give it more.
two
Answer: I would say around 3 times per 2 months, and if that is too many, breed as much as you can fill!
alot
only once usually one-two table spoons depending on how many gerbils you have.
it has been defended over 500 times
5
Once a week
twice a day!
Don't pick him/her up by the tail. You have to teach them to accept you picking them up. There are loads of tutorials online. Don scare them or chase them around their cage. Give them lots of things to chew and some (not too many!) treats. It takes a long time to do it so be patient and do whatever is best for you and your gerbil.