Can the previous version overwrite the currently installed app?

Question

Suppose the new version of APK of any project is currently installed on the Android phone, but I want to install my previous APK on the phone. In that case, what will happen? Will it be updated to the previous build or showing error?

If it's updated to the previous build, will it only show specific things from that build, or also include the current (latest) things?

Answer 1

Since Android 4.0, downgrading an app is not possible anymore. The installation will fail (with error code [INSTALL_FAILED_VERSION_DOWNGRADE] if installed from ADB).

Normally, app/update uninstallation is needed before installing the specific version from the APK, but doing so will also clear the data. There are alternatives to prevent that:

• For ADB users, adb install -r -d <link to apk> allow downgrading (from an answer by supereee on SO)
• (need root) Use AppDowner to downgrade the app (more detail on AndroidPit)
• (need root) Use Titanium Backup root to backup the data, uninstall the app and install using APK normally, then restore the data (from AndroidForums)

In case of using the first 2 alternatives, only features from that build are available, ignoring the data from newer version. (This may or may not affect the app compatibility)