The rate of information decay is going to vary directly with the rate of physical decay, with special importance placed (for non procedural memory) on the hippocampus (edit: and part of the prefrontal cortex), but there is a lot of memory all over the brain.

Which means that the extent to which the neurons are damaged/destroyed is going to determine the extent to which function is lost. Function and memory are the same thing.

Think of it this way: it's impossible to imagine throwing a ball without using regions of your brain responsible for actually throwing a ball. When you remember throwing a ball the neurons involved in throwing that ball are active.

If you damage the region responsible for remembering the sequence of events that led to you throwing the ball, and/or the regions involved in ball throwing, you won't be able to run the "I threw a ball one time" program.

Regarding freezing and thawing: I don't know but I imagine ice crystals would create some very serious issues.