Demoting 2012 Server:

https://www.interfacett.com/blogs/how-to-demote-a-domain-controller-dc-in-windows-server-2012-active-directory-domain-services-ad-ds/


Windows Server 2016 AD server Prep:

https://www.virtualizationhowto.com/2016/10/prepare-active-directory-windows-server-2016-dc-adprep/



Adding a 2016 Domain Controller to a 2008 / 2003 Domain:

https://www.youtube.com/watch?v=3PYBfjVVxE8&list=FL6mnzYiBslbo0DiJI8R97VA&index=2&t=303s


How to Demote a Domain Controller (Step-by-Step Guide)

https://activedirectorypro.com/demote-domain-controller/