Vivo generally does not provide official tools to unlock the bootloader. Without an unlocked bootloader, you cannot flash a custom recovery like TWRP , which is required to install a custom ROM. Use SP Flash Tool → Read Back to
Understanding the Vivo 1610 (Vivo Y66) The Vivo 1610 is commercially known as the Vivo Y66. This budget-friendly smartphone launched with Funtouch OS based on Android 6.0 (Marshmallow). It features a MediaTek MT6750 chipset. Over time, official software support ended. This left users stuck on an outdated operating system. vivo 1610 custom rom work