I've had to do this before. I took a cube of ice to numb my ear (optional) and just took a safety pin (a sewing needle works too) and shoved it threw. it works wether the hole is closed all the way or partially
If by reopening it you mean re-piercing it, then yes, theres a chance that it'll get infected. If the piercing is healed over, go get it professionally repierced. Scar tissue can be a little tough to...
Sure you can.Ear piercings only go bad, if you don't look after them. Make sure you clean it with either antiseptic or warm salt water twice a day, and with clean hands twist the stud around...