I don't know nothing about the differences between the R4 and other flashcarts as far as how cheats work. But it is pretty easy to add cheats to the R4.
I've been maintaining the R4 cheat database in the R4DS forums, in a thread called, "Post your usrcheat.dat files here!!" for a little while now. As far as I know, it's the most complete one in existence, but I highly doubt it truly is complete. The DL for the one I've compiled is in my sig if anyone is interested. You must use the blank CHEAT.DAT included with the USRCHEAT.DAT for them to work....it's gotten quite large and they don't like to co-exist. Many Japanese codes show as a bunch of ????? though, so be aware of that.