If you have existing content that hasn't changed, there is generally no need to re-publish it. However, when you create new content or make edits to existing content that you want to make publicly available, you should publish those changes.
If you want to build a capability, to do all this programmatically you can refer to these articles :
Did not quite get your question. But from what I understand, if the same content exists on your Publish instance and author instance then no need to publish it again. Once you edit the page content or properties you need to publish the page again so that the latest content reflects on the page.
Let me know in case of any further questions. Happy to help.
If you have existing content that hasn't changed, there is generally no need to re-publish it. However, when you create new content or make edits to existing content that you want to make publicly available, you should publish those changes.
If you want to build a capability, to do all this programmatically you can refer to these articles :
