I am working from India for a US company and as per my knowledge I am
not liable to pay any tax to US govt.
Says who? When the IRS comes knocking to you (or the company that pays you, more likely), what will you pull to show them? Verify with a licensed EA/CPA (licensed in the US, of course) if it is true, and based on what. Generally, income sourced in the US is taxed by the US first, before anyone else. It might be that you have to look into the US-India tax treaty for answer.
My first question is can I have them deposit my pay check in US
without any deduction of taxes. I think I need to fill W8-BEN form for
That depends on your status with the employer, and the answer you get from the licensed US tax professional regarding the taxation on the moneys. If indeed it is not to be taxed by the US - you have to provide W8-BEN or W8-ECI (your licensed US tax adviser will tell you exactly which of them you need), on which to specify your exemption claims and what code section they're based on. The employer will then withhold accordingly.
Your second question has been answered by Dheer, so I ignore it.