Hello,

In the case you didn’t know, since Windows Server 2008, you can rollback your Domain Functional Level in certain conditions, if you look at this link, you’ll get all the details :

http://technet.microsoft.com/en-us/library/understanding-active-directory-functional-levels%28v%3Dws.10%29.aspx

Here a recapitulation :

And if you activated the “RecycleBin” :

Note : The rollback can only be done with PowerShell “Set-ADDomainMode” cmdlet from the ActiveDirectory PowerShell module.