Hi! Thanks for the question!
If one wants to sue upon someone in India, and if you are not in a position to come to India and appear in the court at the time of suit/Filing, you may send a duly registered/Notarized power of attorney in favor of a competent person in India for filing the plaint on your behalf. BUT, in future of the court thinks that your presence in required at some stage, then you will have to come, persue your case.
Normal, legal size paper is required in the courts of India. The Green Paper , that is a water mark is not a compulsion. If it is available you may use it. It used to be necessary earlier. If any other documents have been sent from the foreign country, then they should be as per the rules of the foreign court and should be duly gone through the registration process through embassy or any other concerned authority and should be duly attested!