Question [Q] CM 11.0 (Kitkat 4.4.2) downgrade to stock ROM?

I have CM 11 flashed on my phone that is rooted. I wanted to downgrade back to any stock ROM for SIM card unlocking purposes. Obviously the CM 11 does not allow SIM card unlocking even with valid unlocking code.

My question is, is that possible? I think the CM 11 upgraded the modem and bootloader, which means there is no way back to older versions.

Can someone please provide some insights? Below are the settings of my phone: