Unlock bootloader for Tecno Spark 10C - K15k

I am trying to unlock the bootloader of my Tecno Spark 10c to install custom ROM on it.

C:\Users\Monami and Agnibha\OneDrive\Documents\tecno_root\platform-tools>fastboot flashing unlock
FAILED (remote: 'unknown cmd.')
fastboot: error: Command failed

C:\Users\Monami and Agnibha\OneDrive\Documents\tecno_root\platform-tools>fastboot oem unlock
FAILED (remote: 'Unlock bootloader fail.')
fastboot: error: Command failed

C:\Users\Monami and Agnibha\OneDrive\Documents\tecno_root\platform-tools>fastboot oem unlock-go
FAILED (remote: 'unknown cmd.')
fastboot: error: Command failed

C:\Users\Monami and Agnibha\OneDrive\Documents\tecno_root\platform-tools>fastboot flashing unlock_critical
FAILED (remote: 'Not implement.')
fastboot: error: Command failed

C:\Users\Monami and Agnibha\OneDrive\Documents\tecno_root\platform-tools>

I have tried everything, and every command, stack forum, and other website doesn't help. Please help if any experts are there.