You assume all risks. If steps are not followed correctly, it may lead to a bricked device.
Tap on or Build Number 7-8 times until you see the message "You are now a developer." Go back to Settings > More Settings > Developer Options . Enable USB Debugging . Enable OEM Unlocking . Phase 2: Unlocking the Bootloader on Vivo Y71
If you are looking to install a custom ROM, I can provide steps to (like TWRP) next. Just
This process voids your official manufacturer warranty.
Re-enable using the method described in Step 1.
Execute the command to reboot into fastboot mode: adb reboot bootloader
Boot the phone into stock recovery mode (Hold Volume Up + Power). Select Wipe Data / Factory Reset , clear all caches, and reboot the system.
Check your phone screen; a prompt asking for USB Debugging permission may appear. Tap Now, boot the phone into Fastboot mode by running: adb reboot bootloader
Unlocking the bootloader on your Vivo Y71 comes with some risks, including: