Customization that require change in the code, and the upgrade

These need to be exported into a custom app then. You can try this:

  1. On your current instance, follow these steps

  2. Initialise this app as a git repository and push it to the online repo.

  3. Now on this new installation, you can clone your app and install it on the currentsite.

This way, all the exported features will be created in your new installation.