About 100% of the time as long as the "damage" you are trying to fix is stain on products case and has nothing to do with electronics. Cleaning is not fixing, you cant clean your way into a reliable repair.

DI water can prevent damage to a product that has gotten wet but not yet short circuited, but once something has shorted out, it's most likely too late.

In theory, yes, in practice, no. I have short-circuited MCUs at 3.3V many times due to incorrect reflow soldering, and after reheating they still worked fine.