[KeyofBlueS]

Pandora can install 3.60 M33 on PSP Slim but can't unbrick or downgrade PSP Slim.


From 3.60 M33 Readme

Сообщение от M33 - Press L+R+triangle to uninstall M33 and go back to original 3.60. Note: this can't unbrick a psp slim, it will just remove M33 ipl. There is currently no unbricker for the psp slim, but we plan on doing one in the future. After uninstallation, psp will be shutdown automatically.

and

Сообщение от M33 Q: How can i unbrick the PSP Slim? A: if you have a semi-brick, you can restore it using recovery and flashing the corrupted files with usb flash. There is no real unbricker for PSP Slim yet, but we plan of doing one in the future using C+D Pandora Battery.

Installer of 3.60 M33, that it uses Pandora, don't downgrade anything. "Simply" replace the original prx with custom prx's and IPL.