H4 Dropbox eligibility

[mari_a]

I'm planing to bring my wife and kid to US. My wife already have H4 Visa valid till Sep 2018 filed by my ex employer. My kid doesn't have any visa. I have recently changed my employer and got an I-797 approval notice till April 2020. I know my kid is eligible for drop box. I'm planning to get my wife stamped again, so that she could get her visa till April 2020.

Does my wife is eligible for drop box?
Does employer change require the dependent to appear for visa interview?

Please advice.