Stick with Android 11 ROMs for the Vivo Y51. Android 12/13 ROMs exist but suffer from memory leaks on 1GB/2GB RAM variants.
Custom ROMs allow you to install versions of Android (like Android 12, 13, or 14) that may not be officially released for your device. However, this process carries risks. vivo y51 custom rom upd
You lose VoLTE (in some regions) and the stock camera quality, but you gain contemporary Android features, monthly security patches via open-source maintainers, and a pure Google experience. Stick with Android 11 ROMs for the Vivo Y51