Jailbreaking 3gs 4.2.1 & keeping current baseband 5.15.04
I have a 3gs new bootrom (model MC136LL, serial # ***15******) modem firmware 05.15.04 currently restored & updated to iOS 4.2.1
I want to jailbreak & unlock it without upgrade to the ipad baseband 6.15.00, is there any way I can do that? I hope to keep my current baseband due to many problems occurred with 6.15.00.
If there is currently no solution, can I downgrade my iOS to 4.1 or some lower OS without any SHSH saved?
Thanks for all your help.