Travel after applying H1B extn

[vr1980]

My H1B is expiring 9/20/2017, I have a valid US visa that's valid until 9/20/2017. My employer is preparing to file the extension. I have plans to travel to India mid may to July 4th. This is the second extension after 140 approval. Questions:
1. Can I travel outside US after applying H1B extension?
2. Should the employer file extension after I come back.
3. Can the employer file extension while I am outside US.

Thanks
Venkat