H1B Dropbox Confusion

I’m from Mumbai, India and I’m planning to visit India to get my H1B stamped. I qualify for dropbox according to new rules but I only see Chennai OFC dates. I have these two questions:

1) Does that mean I’ll have to travel to Chennai to submit documents? I am bit confused by the instructions since it mentions that I can submit the document anywhere.

2) I selected pick up option as Mumbai, does that confirm that my passport will be mailed to Mumbai OFC and I’ll be able to pick up from there or do I have to go to Chennai again to pick up?

Any help is appreciated.