If you cannot get a stable TWRP working, consider these alternatives:
You should see your device serial number. twrp vivo y71 full
Vivo phones come with a locked bootloader and do not officially support unlocking. Installing TWRP on a Vivo Y71 requires unofficial, often risky methods (like using test-points or modified boot images). This can brick your device, void your warranty, and break Funtouch OS OTA updates. Proceed only if you understand the risks. If you cannot get a stable TWRP working,
Installing TWRP and flashing custom ROMs and kernels may void your device's warranty and potentially brick your device. Proceed at your own risk. void your warranty