Flash step's Redmi 9 (lava):

The main method:

- Make an imei backup!

- Download rom

- Wipe dalvik/art cache, cache, data, and data for yes.

- Reboot to recovery

- Flash in FW

- Flash in ROM

Optional:

- Flash Magisk, GApps, etc.

Alternative method:

For those who do not trust these installation steps, flash the 12.5.1 global version of MIUI on android 11 via fastboot, after installation, delete Dalvik / Art, Cache, format data and data separately via yes, reboot into recovery and flash the ROM.