Have you tried it?
You can not add more vCPU than logical cores.
You can't fit a 200lb man in 100lb pants.
You can only create as many vCPU as you have logical cores available.
Overcommitting memory in general is possible, 100% is not a good idea though, as it will lead to heavy swapping and a terrible performance.
Thanks for the info but does the same behaviour exist in VCloud director environment since in Vcloud director the resources presented are in resource pools which the total resource could be more than a single physical server
No it does not work in vCD either.
You will also be bound to your organizational resource entitlements.