You cannot install a custom ROM without unlocking the device bootloader. In 2018, Huawei officially stopped providing bootloader unlock codes. To unlock the Y7 Prime 2018 today, you must rely on paid third-party software tools (such as PotatoNV or DC-Unlocker) or physical test-point methods that require opening the phone casing. Project Treble and GSI Support
Your phone is 8 years old. The warranty is long dead. Don't worry about Knox or e-fuses—Huawei doesn't use them like Samsung. huawei y7 prime 2018 custom rom better
Note: Avoid selecting "Internal Storage" if your downloaded custom ROM installation package is saved directly on the phone's internal storage media rather than an external MicroSD card. Step 4: Flash the Custom ROM and GApps You cannot install a custom ROM without unlocking