roll back to WP 8.1 with out Windows Device Recovery Tool

[sadegetouha]

hello i have att go phone and its unlocked

and supposed to be de-branded by that method
https://www.reddit.com/r/windowsphone/comments/4bcvgg/comprehensive_guide_to_lumia_640_unlocking/

with out flashing any rom and i go to W10m using Insider with slow ring then change to production ring

now i download att file rom from lumiaframeware and i need to roll back to WP 8.1 with out and then flash PackageTitle: RM-1073 VAR LTA 7R CV
Product Code: 059X153
cuz i don't need att stuff in my phone
i really glad for your help thank you