well i had 6.38 downgraded to 20 and used ProB-7 recently upgraded to 8(less bugs) with this i dont use nitepr wish i knew how to install it made many attempts all failed..... but coderpr is a good plugin to use.
So a compiled list.
1st. Downgrade to 6.20 using:
6.20 update file/Downgrader. Download: [You must be registered and logged in to see this link.]
2nd. Downgrading. Okay so place the downgrader folder(downloaded in 1st step) in the GAME folder of your psp: K:\PSP\GAME
Place the 6.20 update file in the Update folder K:\PSP\GAME\UPDATE.
Now go out of usb mode go over to the game tab and run the downgrader.
3rd. Get 6.20 ProB-7
Source+Download: [You must be registered and logged in to see this link.]
4th. Activating ProB-7.
Okay once you download the 6.20 version place all of the folders except SDK folder and Text file.
In the game folder K:\PSP\GAME
5th. Now that you have placed the files do the following: Leave usb mode and Go to game tab. Go down to The updater(this enables the CFW) Run that and hit X. Give it a few and it will reboot. Now this is very important. Run the Permanent Patch. It will say some things the first option, Do the this Hit X then more things will appear. Hit X once again. If your PSP restarts that Means you are able to run the CFW permanently. Now run The permanent patch once again BUT THIS TIME, Hit X at first option Then HIT O
at the second option. Let it work its magic, then go check what your firmware in system settings. if it says 6.20 Pro B-7 then you did everything correctly.NOW THAT WAS THE HARD STUFF
Now the easy things
7th. Get CoderPr. using: [You must be registered and logged in to see this link.]
Just hook your psp to your PC select the removable disk it is, and put that as your removable disk on the installer easy as that.
8th. Activating the CoderPR.
Okay after you do step 5. and you installed the CFW. do this. get out of USB mode and HIT SELECT a menu should appear go down to RECOVERY MENU using the D-pad and Hit X, Go to Plugins and ENABLE coderpr.prx then exit Recovery Menu. then go into FTB2 or what ever game you want to cheat or hack in, and there should be a message in top left of the screen. Double press home the HIT the - and + at the same time then a screen will appear hit START and a cheat list will appear hit  to enable and disable the cheat. then hit O to close the screen. To view cheats again hit - and + again.
Okay now to get new databases. for games heres my DataBase for FTB2 these codes are all no 35 which means NO BANNING.[You must be registered and logged in to see this link.]
Place here K:\coderPR\cheats this is where you would place all your cheats.
Hope I helped THANK OR REP ME or what ever you do If I helped.
If you need more help feel free to ASK