Can I interview for dropbox if eligible and traveling?

[LarmanKhemka]

I have a few questions for this group:

1. Can I still interview for my visa if I am eligible for dropbox? I have travel plans in July and it seems that interview dates are more accessible.
2. I have misplaced my old passport with my previous F1 visa. The questionnaire only asks about the loss of the 'most recent' US visa. Should I mention the lost passport and visa?
3. Do I need to submit both my old and new passports for dropbox processing?
4. What is the current estimated waiting time echat to koows receive the passports after using the dropbox facility? I would greatly appreciate any assistance provided.