Thanks for the response!
So to clarify: It’s not possible to prevent PR’s from being merged in multiple Azure DevOps organizations if you only have developer license?
If you need to configure multiple instances, then you’ll need Enterprise Edition. The internet is telling me that organizations (can) exist within the same instance, so I believe you’ll be good with Developer Edition.
I am not sure I understand. I was under the impression that ‘instance’ and ‘organization’ in Azure DevOps were interchangeable. In DevOps you can have multiple projects under the same organization, but as far as I know there is no entity to combine multiple organizations.