Applied H1B extension and travel before expiry of current visa

[Santhosh Kumaresan]

Hi

My Current H1B Visa Expires by December 19 2013.

And i have applied for extension by August 5 2013.

Now i need to travel India for an emergency and i will be back in a week.

1. Please let me know if i can travel while i have applied for extension? If so what document i should carry while returning to US?
2. Please let me know before which date i should be back to US(Considering current visa expiry date December 19, 2013)?

Thanks in Advance.

Thanks
Santhosh