Hyper-V enables running virtualized computer systems on top of a physical host. These virtualized systems (aka: guests) can be used and managed just as if they were physical computer systems, however they exist in a virtualized and isolated environment.
You can rename a Hyper-V virtual machine anytime you like.
When you rename a Hyper-V virtual machine, it will only change its name in Hyper-V Manager. It will not change the name of the folder or virtual hard disk (.vhdx) file(s) for the virtual machine.
This tutorial will show you how to rename a Hyper-V virtual machine on your Windows 10 PC.