h4-h1b COS process and time lines


I have H4 visa as my wife dependent. My wife is currently working in U.S. with H1-B.Now My H1-B petition got approved.

I would like to travel on H4 to U.S. and apply for COS from H4 to H1-B.

My doubts are:1. How long the COS process takes at current situation?2. For COS, what documents my employer should provide?3. which one do you suggest? First travel on H4 and move to COS? or Try for H1B visa stamped in india itself and then travel? 4. Suppose if my H1B visa stamping is not successful then is my H4 valid ? can i travel with H4 then?

awaiting for reply.