Hi Ashish,
Being that this is an old thread, could you create a new one for the AuthorizationError.USER_PERMISSION_DENIED issue that you encountered? We can continue our discussion from there.
As for the Labels related issue, I have already replied privately earlier to your email address. This being said, you may check if you have received my reply, and you can also respond to me via that email if you wish to discuss that issue further.
Best regards,
Peter
AdWords API Team