I am currently on Blanket L1A with following dates -
Visa Expiry - Aug 2016 (still valid)
I94 Expiry - Dec 2017
My visa extension is in progress and company would be filing it before the expiry of Visa.
My question is -
> I have heard that USCIS allows visa extension to be filed up to only 6 months in advance. Is this a USCIS directive or requirement. All I could find on USCIS site is visa extension should be filed at least 45 days before I94 expiry.
> Does this mean that USCIS will reject my visa extension as it will be 1.5 years before I94 expiry.
> If I need to go back to my home country, will I need to get a fresh visa application filed before I can enter US again?
Thanks in advance.

There's no such thing as visa extension. A US visa is only for entering the US, and as such can only be gotten at a US consulate abroad. If you need to travel abroad and return after the expiration of your current visa, you would get a new visa before you return. The visa has absolutely nothing to do with your stay in the US. You might be thinking about Extension of Status.

Your status currently lasts until December 2017. There is no reason to apply for Extension of Status so far ahead of time.

Regardless of when your status expires or whether you do Extension of Status or not, if you need to leave the US and re-enter after August 2016, you will need to get a new US visa when you are abroad.