Mental Harassment by one of the building resitent

My building in which I am staying was constructed in 1990. My mother purchased the flat in year 2003 and was told the registration for the housing society was filed and its proposed by the one of the resident A K Saha who claimed to be the secretary of the building. However years passed but to information on the registration was given and we also did not question it. Since few years now the this person A K Saha had started a school and a cancer patient home in the building without asking other owners in the building. Since the other owners do not stay in the building or have rented the flats, my family protested against him. Since then he has been harassing us by the mean of not giving water in timely manner and has stopped out access to the terrace by locking it. We have complained against him to police. However he abides by it for few days then starts again. He one also used some one else to make complaint against us for harassment to which the case was dismissed as no offense. Even after police giving him warning he still continues to lock the terrace and has asked people not to give us keys. The other owners of the building are least interested in the issue and hence do not want to come forward. This person A K Saha claims he is the secretary but never produces any kind of record or approval on the same. My queries are : 1) As a owner on the flat in the building which is not a registered housing society what are my legal rights on the building amenities. 2) What are the legal way that I can approach to get this issue resolved. 3) How can I find the construction year of the building. 4) Since I know the building I stay in is very old, where can I complain for its structure stability.