Company A filed my H1-B Visa and I came to US. After 1 year, I moved to Company B and I have been working here since 2014. I visited India and got the stamping done with Company B.
My wife was on H4 and she got her H1-B in the year 2015. She did not travel to India after she got her H1-B Visa. Her previous H4 Visa is also expired.

She just worked for 1 month since Oct 2015.
Now, she is traveling to India for an emergency and while coming back she wants to get H4 Visa stamping done.

Question 1: Can she travel to India now and get H4 Visa stamping done?
Question 2: What supporting documents does she need to carry with her to get the H4 Visa?
Question 3: Does she lose her H1-B Visa permanently, if she get the H4 VIsa (or) Can she change status to H1-B again in the future?