How to cancel/close the other running VM consoles?.
With vCenter Server you can use the vSphere Client -> Administration -> Sessions to terminate sessions.
How to deleted the unwanted VM’s and how to restore the accidental VM’s & objects?.
In the vSphere Client, power off the VM and then right-click on it. Choose the Delete from Disk option. I usually verify the VM's working location (directory) has actually been removed afterwards, as sometimes objects will linger. Restoring will depend on how you do backups. What can you tell us about that?
How well we use the vApp in real environment?
Things like tiered apps are a good example of a use case for vApps.