Huawei devices often rely on proprietary vendor files (radio/modem firmware, camera libraries). When upgrading Android major versions, you may need:
: Huawei stopped providing official bootloader unlock codes years ago. You will likely need a third-party service or specific technical tools (like PotatoNV or DC-Unlocker) to unlock the device before you can flash a custom ROM. Project Treble huawei y7 prime 2018 custom rom better