Is drinking water with adding few drops of hydrogen peroxide safe? i heard it protect u from flu and other contagious diseases...

No: Fda says don't do it: http://www.Fda.Gov/newsevents/newsroom/pressannouncements/2006/ucm108701.Htm. Yes it's useful to decontaminate a wound or sterilize a toothbrush. Some might even rinse their mouth but i haven't seen any published studies suggesting benefit. I certainly wouldn't drink it.

Not true: A couple drops of hydrogen peroxide in a glass of water will do absolutely nothing. It will not protect you from any disease if the water or glass is contaminated or if you are already sick.