MS0, MS0, MS0... WHEN WILL YOU EVER LEARN!
Hacking gets you NOWHERE in the world of proprietary hardware! Sony works SO HARD trying to legitimately give you a ton of fun games on PSN, so if you were foolish enough to attempt cracking into such an expensive and gorgeous device JUST so you can make a STUPID FREEWARE GAME, you really deserve this mistake.
My suggestion? Ditch firmware. If you want a PSP, use it the way it was made to be used. If you want to make a game, join Microsoft's XNA Studio Club.
I'm sorry if this sounds rude, but this is all I can say. I have had a WONDERFUL experience with my PSP, and I never had to fiddle around with "batteries" or "downgrades" or any of that crap!