H1B & H4 Extension: Drop box eligibility

[CodeMad]

I'm in the United States on H1B and my wife on H4. We are here over the last 1 year and recently got our VISA extended for 3 more years. We have a plan to visit india sometime soon and have to get VISA stamped in India before re-entering to US. Here are the questions.

1. If I change my employer before my travel, Are we eligible for drop box extension? (So that we are not required to appear in person)

2. What If I send only my wife to India for a visit. Since she is on H4, is she required to go in person for the VISA interview to get it stamped If I change my employer?

3. What are the chances of delays in stamping (i.e. Putting it under Admin Processing etc) that creates delay with my return. Generally, Is it advisable to go to India post your H1B approval here?

Best,

CodeMad