The first question I can't really help you on. I know it has one once opened, but not sure about unopened bottles. As far as hydration bladders, I've used Potable Aqua tabs in my Camelbak for just over 40 bag nights and haven't had any problems. The iodine does stain the inside of the bag, but after flushing it once or twice upon getting back home, it is (visibly at least) no worse for the wear.

Hope this helps,
Chris.