A: Not supported and not working are very different. Hyper-V is a great example: Many things that will work on Hyper-V, such as running Windows 2000 in a virtual machine (VM), aren’t supported by Microsoft. Microsoft doesn’t support Win2K because it’s no longer a supported OS.
It's very likely that Oracle products will run on Hyper-V (or any other hypervisor) without any problem. However, Oracle only supports virtualizing its products on its own hypervisor, Oracle VM. This is something you need to consider, because if you encounter a problem with an Oracle product on a non-supported hypervisor, you might have support challenges with Oracle. However, you might be willing to accept those challenges rather than run a separate hypervisor just for Oracle products.
In my experience, and after conversations with customers, Oracle support will actually try and help with problems. They generally won’t tell customers to reproduce the problem on Oracle VM, but be aware that it could happen.