Krishna, I did the trip without water filter or treatment. The water spigot at the Bearpaw camp (the commercial one with cabins) had a sign that the water should be treated. I filled up anyway, and continued on. (The signs are required, because they cannot guarantee the water is pure -- like all the other spring and stream water in the park.)
The first day, I made it all the way to Hamilton Lakes but I was really tired. You might consider stopping just before Bearpaw at Buck Creek. It will have water, and it is wide open space. Beyond Bearpaw, there is no water until Hamilton (The crossing at Lone Pine Creek is a deep vertical gorge, so water is inaccessible, ...but maybe a little upstream, not sure)
If you want to get an early start at Crescent Meadow, you might think about taking the last bus the night before, and then finding a secluded spot to just bed down (after dark as long as you are discreet). Half mile in, the trail crosses a gentle crest.
