H1B Petition expired on 1st oct 2017. USA for 1 year and currently in India. Cap exempt or not?

I got the H1B petition from 1st oct 2015 to 1st oct 2017. I worked in USA from Jan 2016 to April 2017.

Now petition is expired and not in current future any project work from my current employer.

Is it possible to get my extension? My Petition is now invalid.

Can I start look into change my employer? Will it be safe to go for visa extension interview with amendment on expired petition?