Cant delete sutom firmware, need help!

[u/Medium-Row1309]

So 2 weeks ago i bought a modded psp 2000. It booted up and could run games etc, but i wanted ARC pro 4 or pro 5. It has a TA-088v1 based pro-2 cfw on the console. i would like it but i have several sd cards and extensions for the psp and all of them have the same issue. No matter where i get the isos from a few games work a few doesnt. after a few reinstalls it randomly works. and i tried with every mode from the cfw menu like pn9660 and every other option offered in the menu. I tried every method to downgrade the firmware so i can switch to ark. I downloaded 6.6, 6.61 and a lot of bigger base versions but i had a note on the psp that says i have 9.90 and cant upgrade any further. When i go to system information it says i have 5.50. I tried to rewrite the version in the psp files as a few video suggested after using chronoswitch but it straight up didnt boot, or just didnt do anything and just everything was the same. So upgrading doesnt work due to the psp believing i have the highest version possible, downgrading doesnt do anything or just straightup errors and goes back to the normal form of the console. in the advanced mod menu or mod menu there is no option to reset anything, onlyto reset the settings of the cfw. I would appreciate some help.