I have managed to boot up a 1.5 update on firmware 2.0. Which i edited it to 2.5. but after its booted:
PSP Firmware update 1.5
But then a message popped up: You have a later firmware...ext...
So i need coders to make their own 1.5 "2.5 faked" update so i can run it with my new method, which is by 2 mem sticks, freeplay plz no flamin, and i tried it and it worked, i only need a custom 1.5 (2.5 faked) one.