Widow's rights under Hindu Succession Law.

My father died on 25 June 2005 and he had not made any will. He has four children - two son and two daughters and our mother. My both sisters married in 1990. After death of my father we, four children gave NOC to transfer the flat on my mother's name. Now mother and my big brother did some papers and transfered my father's flat, light bill, ration card and gas connection on my big brother's name, without taking any legal permission or informing other heir. Now my question is - 1. Do we have any share in my father's property after giving NOC to mother for transfer the flat on her name? Does my Mother become legal owner of my father's flat? 2. Can Society transferred the rights without taking any legal permission from us? 3. Do my sister have any legal rights in my father's property, because Girls rights act came in Maharashtra from 1994 and my sister's marriage happened in 1990 before the Act came in? Also in all over India it came in 9 Sept. 2005, and there also condition is father and girl should be alive on the 9 the September then only the Girl can get the rights in father's property?