My case got selected in lottery,Can i travel to US on h4(i have valid h4 till sep 30) after h1 is approved and then apply COS from h4 to h1 or is it risky and I need to travel on h4 before H1 approval itself,do i need to go to stamping if h1 is approved when I am in india even though I have a valid h4 stamped in passport to enter US
Yes you can travel on H4 even if your H1 is approved.
As long as you dont intend to work in US with your H4( as you are on dependant VISA) there is no need to get your approved H1 petition stamped.
I am not sure how risky it would be to apply for COS from h4 to h1 when you are in US but surely if your papers are fine and as long as there are less number of Vendors( E-V-C model preferably) between you and your employer chances of getting COS approved smoothly is more.
You have 2 options - get H-1 visa stamped and return on stamped H-1 visa after Sep 20th and be on H-1 status from Oct 1; or enter on H-4 visa and file for H-1 COS.
Talk to your employer/attorney about their recent experiences w/ H-1 stamping and COS. Generally COS is easier than stamping, but you cannot work on H-1 until COS gets approved (H-1 visa stamped if approved allows you to start working as soon as you enter US).