Sometimes an app update comes along and you wish you stayed on an older version. Sometimes it’s just not as simple as uninstalling your current app and installing the older APK again, as maybe you have data within the app you want to keep or it’s a system app and you don’t want to fully uninstall it. Thankfully due to the capabilities of the Android Debug Bridge (ADB), it’s possible to downgrade an app version without requiring root and keeping all of your data.
A prime example would be WhatsApp, which to use Substratum themes usually requires a certain version requirement. Rather than having to uninstall WhatsApp and go through the pain of logging into your account again, you can simply use this tutorial to downgrade again, using only adb. Root users may prefer to use something like App Downgrader on the Play Store. If you wish to proceed, firstly grab either Minimal ADB & Fastboot or the official Google binaries containing adb.
How to Downgrade an App on Android
Find the APK of the app version you want to downgrade to. I recommend looking for it on XDA Labs or APKMirror. Open the folder containing your adb tools, open your command prompt and navigate to the folder containing adb. Copy your apk file that you wish to downgrade to into this same folder where you have the adb file as well.