How to Downgrade from Android 9.0 to Android 8.0

[Android Central Question]

Recently my Galaxy S9+ got upgraded to Android 9.0, the interface of which I don't like. I have turned-on "Back up My Data" for my Google account.

Now if I do a Factory Reset & Restore my Backup will that be good enough to downgrade to Android 8.0 ? Kindly advice.

 

[mary beth hale]

You cannot downgrade to Oreo once you've updated to Pie by simply factory resetting.
You can flash the phone back to Oreo using Odin.

 

[Mooncatt]

Even if you did downgrade, the phone will just update itself again unless you take additional steps to prevent it. On some phones it's as simple as ignoring the update notification (like on my wife's S7), others may require rooting the phone.

 

[Deepcuts]

Recently my Galaxy S9+ got upgraded to Android 9.0, the interface of which I don't like. I have turned-on "Back up My Data" for my Google account.

Now if I do a Factory Reset & Restore my Backup will that be good enough to downgrade to Android 8.0 ? Kindly advice.

Had the same question: Found the answer and explained in simple steps here: https://forum.xda-developers.com/showpost.php?p=78923346&postcount=13