JiaYu just released the Android 4.1.2 firmware for G2 single core version yesterday.
Due to the two different screens used in G2, there are two version of roms. Please check the software version before you upgrade your phone.
Change Log: Nil
Bug Known: 5MP camera was shown in hardware specification but it will not affect the quality of the photos.
Tools, manual and roms
Read the Manual before proceed !
JiaYu G2 Rom Flashing with Tools Manual (4.1.2)
English Ver. http://www.sendspace.com/file/6yyiol
(Directly Translated to English. Some steps were not given by JiaYu. I don’t know either)
Tools and Drives