Downgrade an app in Nougat

Well, simple. I want to downgrade an app that has been accidentally updated. I've already read [this question](/q/116309) but it didn't provide me with a straight instruction. I have the APK I want to downgrade **to** so that question is unhelpful to me. It's not a test package (saved from Google Play) so option -t doesn't make sense. Things I've tried so far: * Run in a terminal (with root)

pm install -r -d old.apk

* Use adb on a computer

adb install -r -d /path/to/old.apk

* Brutally replace the apk in /data/app and manually run dex2oat to force compile it All of above were to no avail. So I'm quite bothered about this. I don't want an answer telling me **uninstall the new app, then install the old one**. I want to retain app data without backing up.