Can I get some help please?

Hey guys!

So lately I got a ps vita and I was doing some research about how you can download demos with another region's PSN by reformatting. I currently use a American psn and I switch into a Japanese account I made. Oh btw I don't know any Japanese at all. Now here's my story. I've downloaded demos from the Japanese psn store and switched back into my American account and the demo still runs perfectly. While I was in the Japanese psn store I happened to have found the project diva games for download. Can I still download then and switch back to my American account and still play it like the demos? Would it still work? I know the vita is region free . Please give me some advice back guys! Really want to play some of these games. ^_^