Downgrade the Forest Functional Level
Step 1. Open PowerShell with elevated privileges.
Step 2. Execute the following command, replace the identity with your domain name and the forestmode with the level you want to downgrade to.
Set-ADForestMode –Identity “CANITPRO.com” –ForestMode Windows2008Forest
In the above example, I have downgraded the forest functional level to Windows Server 2008.
Downgrade the Domain Functional Level
Step 1. Open PowerShell with elevated privileges.
Step 2. Execute the following command, replace identity with your domain name and domainmode with the level you want to downgrade to.
Set-ADDomainMode –Identity “CANITPRO.com” –DomainMode Windows2008Domain
In the above example, I have downgraded the domain functional level to Windows Server 2008.
To confirm, execute the following commands
Get-ADForest Get-ADDomain