Firmware.

Is it possible to flash a PS3 Super slim cech-4208c?
Here I found a way to downgrade, but I doubt it is working.
http://ps4portal.net/ps3-downgrade-to-3-55/
Here she is referring to the website. The version of my firmware 4.82
And Yes, on the website(see above) write that method works on super Sliema, is this true?