Regarding: non judicial stamp paper

I have two queries: 1. can any advocate buy the non judicial stamp paper in his/her own name/own firm name if that stamp paper is for power of attorney in favour of the that advocate himself/herself? (power of attorney to represent the client or act on behalf of the client). what are special requirements to buy if it is allowed to purchase in own name; like to write in register on behalf of or with authority from the client etc... or any other formality? 2. is any power of attorney stamp paper which bears the purchaser's name on its rear side and having seal/signature of the stamp paper vendor, but not signed (not having sign) of the purchaser; valid? Does having no signature of purchaser not invalidates the poa/stamp paper (as purchasing stamp paper itself is a sale and purchase under relevant act which is signed between stamp paper vendor and purchaser and rear side of stamp paper is very important for the validity of stamp paper); and will it not make stamp paper void and invalid if it is not signed by the purchaser at the rear side / back side of the stamp paper?