If there was a natural disaster...

Question

and all I had was a bottle of peroxide, could I boil and/or expose it to intense light, wait for it to decompose into water and oxygen, and then safely drink it?

Answer 1

better off going thirsty and using the peroxide to sterilize wounds etc.

Answer 2

Not really.  Yes, there would be water present, but it is unlikely that the peroxide would completely break down.  Not only that, the end product would surely contain dangerous reactive oxygen species which could cause many problems by breaking down the proteins in your body and causing mutations in your DNA that could lead to illness down the road.

.........I'd just keep a bottle of water on me instead.