Is it possible to run completely different operating systems on Virtual Machines $($VMs$)$ that are on a single host? If yes, what makes this possible?

No$,$ it is not possible$$A single host can only work as one single virtual environment, and can, therefore, have only one environment.

Yes, Virtualization makes it possible$$ to have VMs$,$ running different operating systems, on a single host.

Yes, Containerization makes it possible$$to have VMs that are unique physical entities, so you can have completely different Operating Systems on them.

No$,$ it is not possible$$VMs are software$-$based versions of a single host. They cannot have different environments from one another.