You cannot cross-flash certain variants without unlocking the bootloader. For example, installing China Firmware on a Global device will lock your system language to Chinese and break Google Services unless you know what you are doing.
Do not download firmware from random Telegram groups. Use trusted databases: Firmware XIAOMI 12
Always check the firmware version number. you want the EEA modem firmware
A specific variant for the European Economic Area that complies with EU privacy regulations. Firmware XIAOMI 12
If you use a Xiaomi 12 on T-Mobile (US) or Vodafone (UK), you want the EEA modem firmware, not the Global. The EEA firmware has stricter SAR (Specific Absorption Rate) limits, preventing the phone from overheating when switching between LTE and 5G on the X65.