H1B Amendment in Premium Processing same employer

I have stamped H1B for my existing employer and currently based out of India( never travelled to US). My employer has filled H1B amendment under premium processing for project and location change. Its a client project and client letter has been shared in petition. My existing visa is valid till Dec 2015. I have the following question:

  1. How much time will it take for amendment under premium processing ? My case was shipped to USCIS on 21st Aug.

  2. Will I receive a new case/receipt number or it will be same as was provided during 1st petition filling.

  3. Do I qualify for Dropbox visa stamping ?

Thanks for proving your response.