Hi,i bught a version 2.7 psp and its code is 1c6001 can it be downgraded to 1.5 safely, plz help im confused?

thers a psp with ta082 code and it dosent downgrade if u try it it breaks, is my ps2 ta082 and can sumone tell me how to downgrade and if i do can i still play umd games to 1.5, thanx