Planning to go for H1B and H4 visa renewal stamping

I am on H1B visa and my wife is on H4 visa. Last year (2021), I changed company and my H1B transfer and my wife H4 renewal was done by my new employer.

We are now planning to get VISA stamped by going to India and scheduling an appointment in India. Few questions regarding that:

  1. In terms of applications, do we need to fill 2 DS 160 form and then create on CGI profile for myself and in that, I can schedule appointment for both of us. Is that right?
  2. As it is more than 1 year since we got our I-797 Approval notice, are we still eligible for dropbox appointment? I heard that there is some extension of 48 months as compared to 12 months earlier.
  3. In Dropbox appointment, do we need to schedule for 2 days for biometrics and dropping the documents? Or just 1 day?
  4. How much time on average does it take after dropbox appointment to get your passport back?
  5. My old Indian passport has previous H1B and similarly my wife previous H1B is also on old passport. The old passports for both of us are expired. So, while filing DS 160 form, should we give information for the new passports? And at the time of dropbox, do we only need to submit the new passports?
  6. How does I-94 gets updated with new passport details. All the current travel history is associated with old passport. Will that history with old passport be moved to new passport when I will re-enter US?