You have to take the green card job to make yourself safe. If you come to the USA and you take the green card job intending to work for this company in the USA on an indefinite basis and with the consent of the company you can apply for a reentry permit. A reentry permit is not a guarantee, but it is a formal declaration by you that says that you are going to live outside the USA for up to two years and not to take your green card away.
A1. I think it is a little risky.
A2. Not from outside USA. You will have to come into the USA.
A3. After you file for your biometrics, it takes about 6-8 weeks to get it done and then you can leave and the reentry permit can be picked up even at your lawyer's office or at any USA address that you have given or at the consulate in your home country.
A4. For green card holders, you can never file taxes as a non-resident. The best thing is because you are living in India we have some kind of a taxation relief treaty with India so that you don't have to pay taxes twice. More...