The Y1S runs Funtouch OS—Vivo’s skinned version of Android. But unlike Xiaomi or even Samsung, Vivo has historically refused to provide official bootloader unlock methods. No fastboot oem unlock , no official token request page.
: The Y1s is an ARM64 device. Download the corresponding .img file. Flash via Fastboot : vivo y1s custom rom
Download the .img.xz file of your chosen ROM. Extract it to get a system.img file (usually 1.5GB - 2GB). The Y1S runs Funtouch OS—Vivo’s skinned version of
: This is the most difficult step on Vivo devices and requires enabling "OEM Unlocking" in developer settings. vivo y1s custom rom