ROM Change

[SAIDREXXX]

I have a Redmi Note 9 (MerlinNFC) with phone operator ROM and I am stuck on the MIUI 12 version. I want to change the ROM through fastboot but I have read that if I select the "Clean all and lock" option I can make my device unusable. What I want to do is change the ROM 12.0.2.0 QJOEUTI to MIUI 12.0.2.0 QJOEUXM and lock the fastboot. Here I have 2 questions:

If I do that, will I get MIUI 12+ automatically and officially?

Is there any risk if I select "Clean and Lock"?