You can clear user data by holding Power + Volume Up to enter Recovery Mode and selecting "Clear Data". Warning: This will erase all photos, contacts, and personal files.
To manually flash the stock ROM, you typically need the following: vivo-y12s-pd2036f-stock-flash-file-firmware-rom
For MediaTek-based models like the Y12s (Helio P35), the SP Flash Tool is commonly used. You can clear user data by holding Power
Navigate to Settings > System upgrade to check for official OTA updates. vivo-y12s-pd2036f-stock-flash-file-firmware-rom