You can't run the VB code on the host directly, but you wouldn't have problems running the VB application on any of the Windows guests that you might have installed on that host.
For your second question, i think you are asking if you can revert a snapshot from within the virtual machine itself.
You cannot do that without some customization. The virtual OS normally doesn't know it has been virtualized and even if it does then you still miss the part to revert the snapshot.
You could add this yourself for example by creating a script that logs in to your esx host using ssh and then run a snapshot revert script (just a few lines of bash ... ) from there.
Personally i'm not a big fan of that approach as it means that your VM can take total control over the host and it would be a possible security weak spot. If this is in a lab then it might be ok.
An alternative would be to use the SDK and a higher programming language OR you could offer access via a browser remote client (mouse/keyboard/video) console or VI Client. The latter two offer decent ways in locking the environment down security wise. Disadvantage is that the remote consoles are resource intensive.
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Wil
