As far as I know you are out of luck, there are no known hacks for Vita FW 3.57. There are no downgrades either. I have a Vita on 3.55 so Im in the same boat except I can play PSP backups on mine. You need to be on 3.52 or lower afaik to do any hacking (at this current time). The real fun starts if you are below 3.36 and then more if you are below 3.18.