The Oreo Beta with December 2017 patch for the Mi A1 weighs in at around 1104.1MB. Android 8.0 Oreo brings along brand new System Interface, Autofill, Picture In Picture, Better Battery Life, Fast Boot, and more.
The Beta is only available for a few Mi A1 users, However Non-Beta members can now install the update in an unofficial way thanks to XDA Developer "rameshurfrnd1". The developer just shared TWRP Backup of his Mi A1 running Android Oreo Beta and the same can be used to Install Oreo Beta.
Note: This procedure is very technical and should be performed by a person with sound knowledge of rooting Android devices. If the step-by-step installation process is not followed properly, there are chances of the smartphone getting bricked or being permanently irreparable. TechDroider cannot be held responsible for any damage or claims from readers if the procedure does not yield the required results or if the smartphone is bricked. Hence, users are advised to proceed with caution.
How to Install Official Android 8.0 Oreo Beta on Xiaomi Mi A1:
Step 2: Save the TWRP Backup file at TWRP/BACKUPS/df0bdeb70404/[UNOFFICIAL] AOSP OREO - tissot Directory.
Step 3: Boot to TWRP Mode.
Step 4: Once entering the TWRP settings menu, clear phone's memory (full) by selecting 'Wipe' option. Once done, select 'Swipe to Factory Reset' perform factory reset.
Step 5: Return to TWRP settings and select Restore Backup.
Step 6: Restore the TWRP Oreo Backup.
Step 7: Reboot your Smartphone.