Out of my bad experiments with 3 of this year's xiaomi phones, here is some things you should consider while flashing any custom Roms
1- you need the latest firmware installed, that can be done either by installing only the small firmware package through recovery or flashing the entire fastboot stock ROM with miflash (be careful not to lock your phone again), ota is good but I don't trust it
2- boot your phone into stock recovery and then use the wipe data option
3- boot back into fastboot to flash your favorite least crashy custom recovery
4- in the custom recovery don't you ever dare wipe system, vendor, cust, or any other thing
You just need to wipe data, cashe and dalvik (might also need to wipe internal for cleaner life)
5- put the RR ROM into the internal memory and flash it (it's better than using sdcard, otg, or even adb sideload but feel free to do as you like)
6 - wipe data, cash and dalvik again please then reboot
........it's very important to know the needed firmware version for each ROM and also if its EU, global or even Chinese
For custom kernels check the supported Linux version
3.** not working on 4.** and vice versa
Sorry for long talk
1- you need the latest firmware installed, that can be done either by installing only the small firmware package through recovery or flashing the entire fastboot stock ROM with miflash (be careful not to lock your phone again), ota is good but I don't trust it
2- boot your phone into stock recovery and then use the wipe data option
3- boot back into fastboot to flash your favorite least crashy custom recovery
4- in the custom recovery don't you ever dare wipe system, vendor, cust, or any other thing
You just need to wipe data, cashe and dalvik (might also need to wipe internal for cleaner life)
5- put the RR ROM into the internal memory and flash it (it's better than using sdcard, otg, or even adb sideload but feel free to do as you like)
6 - wipe data, cash and dalvik again please then reboot
........it's very important to know the needed firmware version for each ROM and also if its EU, global or even Chinese
For custom kernels check the supported Linux version
3.** not working on 4.** and vice versa
Sorry for long talk