If you are looking for the official stock firmware for the Vivo Y91i, you can download it here. The firmware is useful for fixing software related problems like.
- Boot loop
- Un-rooting your phone
- Update firmware
- Restore to factory defaults
- Fix malware/monkey virus etc
Download Vivo Y91i Stock Firmware
Download the stock Android firmware for your Vivo below. Flashing is via MTK Flashtools.