No... you'll simply excrete it faster if you drink too much for your body to handle. Of course, if you drink too much you'll feel nauseated when you exercise.
Yes it is I've seen a few people in the hostpital from drinking too much water. You body literally takes on signs as if it had been drowned (minus the who lack of oxygen thing). Its almost immpossible to accomplish its actually a disease where you continually feel he need to drink water. Normal people would just puke if there body coudn't handle it. You could literally try to drink too much and couldn't pull it off. Its like killing yourself from lack of sleep. Techinically possible but also pretty much techinically impossible. (small rats die in 14 days of no sleep, no human has ever died from lack of sleep) try staying awake that long, even with insomnia you still get enough rest.