Does H4 Stamping requires H1b visa stamp ?


I am currently in US with my employer 2 and the h1b visa I have in my passport is from previous employer.

Can I schedule an VISA interview of my wife who is in india.This will be her first H4 stamping.

what will be the validity if her h4 stamp if everything fine. Is it my old visa validity(Sept 2016) or the new employer petition validty(2019).