New answers tagged downgrade
If the phone is unlocked, then go ahead. It wouldn't matter which carrier that firmware belongs to. As long as it's stock, then you can flash it with no worries.
Check out this website. http://www.freewarelovers.com/android/apps On this website you can find freeware applications and many older versions. Other alternative is F-Droid who allows you to choose which version you want to install. And all available apps on F-Droid are here.
For system apps, there is a way to revert back to the version that initially came with your phone. If you updated a system app from the play store and want to revert the app to the original system version, you can do so by opening it up on Play Store and click 'uninstall update'; this will revert it to a system update. Furthermore you can't even uninstall ...
There is an idea by Firelord in the comment here which I think should work: The best way I think is to have a backup of the app (at least its APK if not the data files; APK of earlier version of an app can also be obtained from some websites (beware of malware) if you updated the app and doesn't have the backup) so that if you end up disliking the ...
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