Can the previous version overwrite the currently installed app? 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?
No, you can't downgrade the app. The installation will fail (with error code [INSTALL_FAILED_VERSION_DOWNGRADE] if installed from ADB).

Normally, you need to uninstall the app/updates, then install the specific version from the APK, but doing this will also clear the data. There are alternatives to prevent that:


If you're using ADB, you can use adb install -r -d &lt;link to apk&gt; to allow downgrade (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 your data, uninstall the app and install using APK normally, then restore the data (from AndroidForums)


In case of using the first 2 alternatives, you will only see the specific things from that build only, since basically you are having that version.