A: Yes, you can create a Windows Server 2012 failover cluster with a single node in it. Typically a failover cluster would have at least two nodes in the cluster to allow resources to actually fail over between nodes in a planned or unplanned scenario. However, it's possible to create a cluster with only a single node in it.
This can be useful for learning scenarios, to look at cluster functionality without having a large hardware investment. It also allows you to take advantage of certain cluster features such as virtual machine (VM) service health monitoring, which can automatically restart a VM if a service within the VM fails a certain number of times.