You'd be able to observe the behaviour implemented by the VM's instruction set, and then you'd know everything you needed in order to write a VM implementation of your own
I don't think you can (necessarily) observe the implemented behaviour (in sufficient detail) as a program running *inside the VM*, for your average (real, computer) VM. Just to pick something at random, the VM might not have any facilities for letting you load new code into it. And even if you can determine the behaviour exactly, knowing that "executing instruction X causes effect Y" doesn't mean you know how to actually implement effect Y in your own VM.
(I'm reminded of Greg Egan's _Permutation City_, which includes some entities who think they're determining the underlying rules of physics but are actually dealing with the behaviour of the VM they live in.)
no subject
I don't think you can (necessarily) observe the implemented behaviour (in sufficient detail) as a program running *inside the VM*, for your average (real, computer) VM. Just to pick something at random, the VM might not have any facilities for letting you load new code into it. And even if you can determine the behaviour exactly, knowing that "executing instruction X causes effect Y" doesn't mean you know how to actually implement effect Y in your own VM.
(I'm reminded of Greg Egan's _Permutation City_, which includes some entities who think they're determining the underlying rules of physics but are actually dealing with the behaviour of the VM they live in.)