Q: Can I mix Windows Server 2012 and Windows Server 2012 R2 Hyper-V with Hyper-V Replica?

A: The only supported mix of Server 2012 and Server 2012 R2 is where the primary virtual machine (VM) is running on Windows Server 2012 Hyper-V, and the replica is running on Windows Server 2012 R2 Hyper-V. This support is there to enable organizations to upgrade without having to break replicas.

A Windows Server 2012 Hyper-V server can't host a replica of a VM running on Windows Server 2012 R2 Hyper-V.