Mi A1 uses A/B system that the Pixel devices use. The A/B systems means that when the device gets an update it will be downloaded and installed on the second system partition and when you restart that second partition will swap to become System A instead of B to make the updating process seamless. The A/B system can probably be altered by editing Boot Image files.
You'll need to Unlock Bootloader and Install TWRP Custom Recovery in-order to Install the Android One Firmware on Redmi Note 4 Mido. You can grab the Custom Rom ZIP file from below.
The Firmware is based on Google's latest Android 7.1.2 Nougat. Additionally, Google plans to roll Android 8.0 Oreo update to Mi A1 by end of 2017, this also means that the Redmi Note 4 will also get Android 8.0 Oreo via Port.