how can you differentiate between RNA or degraded DNA on a 2% agarose gel?
It is very easy. All you do is run the gel and look at the banding pattern. Intact RNA will have 28S and 18S bands while degraded RNA will look like a smear.
Take a look at this website for an example.
I am not sure about the 2% agarose gel but the banding pattern where the degraded DNA and RNA has been run will show differentially as the degraded DNA will remain in double-stranded.