or better uninstall first and then reinstall, so you don't have to increase version, and leave the version changes for release version.
How to Enable Install from unknown sources on Android Oreo:
- First of all, enter into Settings;
- Click on the new Apps and Notifications menu;
- Go to Special Access at the bottom;
- Then, proceed to Install other apps which is also towards the bottom;
- Click on the app you want to allow or block;
- Tap on the switch next to Trust app from this source;
- After that, go back to your app, and tap on the APK file to install it. On File manager app, it’s easy, but in browsers, go to downloads section and then tap on APK file to begin its installation.
So, Google has indeed removed that Unknown Sources switch in Oreo, yet it isn’t the end of the world. Don’t worry, you can still install apps from sources other than Google Play Store.
thanks to : http://androidflagship.com/28497-enable-install-from-unknown-sources-on-android-oreo