Iphone 6s plus downgrade

Hi guys, probably somebody has been asking this but I couldn`t find the answer.

I have an Iphone 6s plus, 128 GB. As some of us, I have enrolled the beta program and played with the phone for a while.

I had enough with the bugs and the battery draining faster than usual, now I want to revert to the normal IOS 11.

I don`t have any backup from the normal IOS, I only have a backup from IOS 11.1 which I did a few weeks ago.

Is there any way I can revert to IOS11, without losing my data ? A guide that I could use ?

I use Windows.

Thank you !!!

Iphone 6s plus downgrade
 
 
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