1. As long as the phone is being charged at 1C or less (IOW, if you have a 2300mAh battery, at 2.3 Amps or less), and it has enough ventilation so the battery doesn't get too hot (don't charge it when it's under your pillow), you're fine. "Fast charge" and "Rapid charge" usually only charge at about 0.75C, so there's no problem.
1. I do that if I'm at 70%, am going to be out all day, don't have my power pack charged and won't be near an outlet all day. Otherwise, it's not unsafe, it's just a waste. (If you leave the charger plugged in, the phone will charge at about 97% for a few minutes, over and over, and it doesn't hurt the battery. It just sits there for a few hours, the charge goes down, the charger kicks in, brings it back to full charge, then turns off and waits until it's down to about 97% again.)