I do a lot of Architecting for my company and it’s often easier to have direct access to DNS to make quick changes rather than wait one or more days for an engineer to go change records. If this is just going to be a test environment perhaps you could delegate a subdomain of your current domain. E.g. Add NS records for test.example.com that point to the NS of the contractors hosted zone. This gives you control to tear it down (delete the NS records) but allows the contractor the ability to build the environment out.

Microsoft publishes a learning platform that covers a large amount of topics, from Windows Server to Azure services. I used it to prepare for an Azure DevOps Database Administration certification. Should be a good place to start as it’s free. Just search for what you’re looking to learn or select a product from the filters and off you go. https://learn.microsoft.com/en-us/training/

If only they had done this with .local ages ago. Still, it’s a nice change, but I doubt my company will adopt.