The only way to downgrade a version 3.52 is by using the "Pandora's Battery". I've written an extensive tutorial about the entire process. You can find it
by clicking right here.
You should make note that you will need a psp capable of already running homebrew in order to downgrade it - at least access to one. Also, you don't need the "lowest" firmware to get the most bang for your buck, but we'll get to that when the time is right.
One last thing, post questions in the "Help" section, and leave this tutorials section for tutorials only. Not a biggie, just be more weary next time.
~moved~
-DarkPacMan77-