A. Each node in a failover cluster supports 32 guests, unless you're using Virtual Desktop Infrastructure (VDI). If you're using VDI, 64 guests are supported on each node. Note that this limit is for each node, and you can have 16 nodes in a failover cluster, so you can have 512 highly available VMs in a single, non-VDI failover cluster.
You can make VDI instances highly available, but that isn't the normal process. If a host crashes with VDI clients, you would simply spin up a new VDI instance on other Hyper-V servers, because all the data is stored outside of the guest client OS.