Download ZTE Grand S II (S291) official firmware from the link here, and follow the provided flashing instructions to learn how to flash the stock rom.
If you notice that any of the links provided below is broken or doesn’t work, please post in comments section so we fix and update it ASAP.
Download Options
File Name: 2015072015023783.zip
Size: 616 MB
Build: 277480B0943ZTE_Grand_S_II_LTE_MEV1.0.0B07
Region: Egypt
Firmware – Download
File Name: 20160801143705531.zip
Size: 510 MB
Build: 271820B0640GEN_IN_Grand_S_IIV1.0.0B06
Region: India
Firmware – Download
File Name: 2014101309570531.zip
Size: 533 MB
Build: 264590B0893APT_TW_Grand_S_IIV1.0.0B06
Region: Taiwan
Firmware – Download
File Name: 2014080817064970.7z
Size: 564 MB
Build: 260470B2008ZTE_CN_Grand_S_IIV1.0.0B03
Region: China
Firmware – Download
File Name: 20160809152844209.zip
Size: 586 MB
Build: 314830B3286ZTE_CN_Grand_S_II_LTEV1.0.0B18
Region: China
Firmware – Download
File Name: 2015121010292565.zip
Size: 587 MB
Build: 300600B3185ZTE_Grand_S_II_LTEV1.0.0B17
Region: China
Firmware – Download
File Name: 2015061514515387.zip
Size: 628 MB
Build: 264350B0584ZTE_Grand_S_II_LTE_MEV1.0.0B05
Region: UAE
Firmware – Download
How to flash
Click here to view complete flashing instructions for any of the above firmware packages. If you have any issue with flashing, post in comments section below for assistance.