My land in dispute

Dear sirs, l am rajendra from andhra pradesh. 30 years back my grand mother bought 200 sq yards land from her neighbour.She didn't take any note from him. She stayed in that place till 2012. Because of heavy strom she left that place and went to my uncle's home. Now she want to build a house in that place .But the neighbour started quarrel with her and he claims for the land as the land adagal having his name. How will my grand mother face him? She doesn't have any documents. She has only house tax bill n power bill recepts from the year 2000 to 2012 . In revenue adagals her neighbour's name is there. So that he is claiming for that land. How will she get full rights on that land. Please help us Is there any G.Os available. Please refer. There is no registered sale excuted by the neighbour/my grand mother. He claims only because of his name is included in revenue adagals. As per my knowledge ,he doesn't have any documents other than adagal copy. My grand mother made the payment by cash only. As her age is not supportive she did a gift deed to my mother, In the year 2013. Now all documents like possession certificate, plan approval from gram punchat has taken in the name of my mother only.Sir, we spent so much money for construction of our house as well as our lawyer. please give a clear picture about the law as our lawyers wouldn't explain.We have taken possession certificate for my mother from M R O.We also took punchat approval for construction of house.In punchat office we got a certificate which stated that my grand mother stayed in that house from 1990 to 2012. Will it supportive to us. we heared that if a person stayed above 12.5 years in a house then that house belongs to him only. Is that correct? Kindly give reply. Thanks and regards Rajendra