Am I eligible for stamping via dropbox?

My original stamped visa [Employer A]: Issue Date: 28 JAN 2013 2012 , Expiration Date: 01 MAR 2015 [Note: I travelled to India and came back to the US before original stamped visa expiry]

Visa extension 1 [Employer A]: Valid from: March 03 2015 TO October 15 2017 [No travel outside the US]

Approved H-1B Transfer [Employer B]: Valid from: February 23 2016 TO Feb 03 2019

After I join my new employer [employer B: Note that I am the 1st H-1B for the company] in April 2016, I am planning to travel to India for a vacation in May 2016.

Am i eligible for dropbox stamping (IWP) in Mumbai? Also, if I do qualify for the dropbox method, is there a possibility of being called for an interview as I am the first h1b case for my new employer?

I would appreciate any responses to these questions.

Your visa stamp expired on Mar 01, 2015. You were eligible for dropbox for 1 year from that date i.e. until Feb 29, 2016. You will be appearing for stamping after that, hence need to go for in-person interview.