A good news for Lumia 1020 users. Lumia Camera app is no longer uninstalled when you update to Windows Mobile 10. This app will remain in your phone when you upgrade from Windows Phone 8.1 to Windows 10 Mobile.
You should use Lumia Camera in order to take advantage of all of the Lumia 1020’s great camera capabilities.
Lumia Camera is not yet available in the Store for Windows 10 devices so you will need to use the Windows Phone Recovery Tool to return to Windows Phone 8.1 in order to get the app back.