u want upgrade version 6.1.2 ? u build 1 FW Custom by Sn0wbreeze (new version). add shsh 6.1.2 because Apple lock sign 6.1.2 should don't restore FW original. then u connect with pc or lap. Put iPhone in DFU Mode (Redsn0w or iReb5+) open itunes. and Shift + Restore choose FW build by Sn0wbreeze (Don't choose fw original) . Then u waiting.
When completed u open evasi0n Jailbreak un.
I wish you success!
My facebook : www.facebook.com/cuong.huynhchi.14