A: The only Windows Server 2012 failover clustering feature to require Windows Server 2012 domain controllers (DCs) is the new ability to use BitLocker to protect Cluster Shared Volumes.
All DCs don't have to be Windows Server 2012, but there must be a Windows Server 2012 DC that can be contacted when enabling BitLocker on the Cluster Shared Volume. That's because the Windows Server 2012 DC has the support for the domain SID-based protector that's used for the BitLocker encryption of CSV.
The Cluster Name Object (CNO) identity is used to lock and unlock the BitLocker Cluster Shared Volumes. The process to enable BitLocker on a CSV is detailed at this MSDN blog post, "How to Configure BitLocker Encrypted Clustered Disks in Windows Server 2012."