H1b 2016 got selected in lottery,, now should I apply for h4 extension?

H4 visa is going to expire on September 30 2015 and I had applied for H1b 2016 which got selected in lottery, now do I need to apply H4 visa extension along with my spouse?

And can I go to india before September 30 2015 and where as my H1b visa is under process,is this possible?

If in case I go to India before September 30 and if my H1b visa is approved, while returning do I need to get stamped on h1b and return on h1b or I can come on current H4 ?

Your answers will be more helpful

Thanku in advance.