H4 Visa Appointment

[shri2400]

Hi,

Question on my wife's visa appointment. 

H4 valid till Dec 2016
F1 valid till Dec 2020

Entry to US - Visa::
Jan 2014 - H4 (went for stamping)
Jan 2015 - F1 (went for stamping)
Jan 2016 - H4 (didn't go for stamping, as H4 was valid till Dec 2016)

India visit planned: Feb 2017

Question:: 
1) Is she eligible for visa interview waiver (for dropbox)??

2) Her most recent visa stamping is F1 (H4 stamping was before F1). But her most recent entry/ current status in the US is H4. Will visa waiver program/ dropbox be eligible if she previously had a H4 visa or is it based on her most recent stamping (F1)