You can get the APK file in the following way.
1. Click System Apps on the home screen and then click File Manager.
2. Click the menu in the top left corner and then click Settings.
3. General settings-->Access mode-->Root Access mode.
4. Go back to click the menu in the top left corner and then click Root folder.
5. Click the data folder and then click the app folder.
6. Find a folder whose filename contains the package name of your app or game. After entering that folder, you will find a file named base. That is the one that you are looking for!
