I got jk2 on Best of PC. Is there any way I can unpatch it from 1.04 to 1.02?
I doubt there's a way you could do that, but why would you want to?
Since your copy of JK2 will always come patched to 1.04, you're stuck with it.
There are allegedly methods of doing this, but they involve making dubious edits to the .exe and in some cases the .dll files, both of which have a high chance of rendering you unable to play multiplayer.
I don't know how, and I don't know why, but this is totally Sheep's fault.