What happens when you click Update after changing content that's part of an app you already published? $*$

Nothing. You have now created a new fork of that content.

The new content will automatically update anyone who has connected to your app

Anyone who has connected to your app will receive a message and they can decide whether to accept the changes or keep the older version

Anyone who has connected to your app will automatically update but they can roll back to the older version whenever they choose