Payment of property tax before possession of flats

Our builder received OC on May30th , 2018 and started possession of flats from August, Sept and very few (3-4) immediately after OC but with incomplete infrastructure or services. Most Flat owners received letter for possession in September 2018 and took possession from Sept 2018 to January 2019. Builder took two years advance maintenance charges for all expenses and possibly for municipal taxes,water charges etc. However ,On formation of society and at the time of handover of charge he is now demanding amount of property tax he paid for 2nd year of advance maintenance amount,as he claims to liable to pay for property tax only for one year out of two years of advance maintenance charges collected by him for period of two years. 1. Can builder ask legally additional amount under the pretext of 2nd year of property tax liability on flat owners. Are owners right in not paying the amount as they have paid advance maintenance of 2 years to builder. and 2nd related question is: 2. This advance maintenance amount period to be counted from the date of OC m( May 2018) received by the builder even as most received possession of flats after September,2018. Builder says that period two years of advance maintenance amount get over on 30th May 2020 as OC is dated 30th May,2018. 3. Society is formed on January, 5th,2020 and society registration obtained by builder is dated 30/9/2019. 4. Builder paid property tax for 10 months of year 18-19 and for 12 months of 19-2020. ( he is now claiming for payment of property tax paid by him for 2019-2020,for which period advance tax was collected by him. Our four questions : Q1. He is now claiming to pay for 2nd year ( 19-2020) of property tax for which he already collected advance maintenance from each flat owner for two years. Can he claim this ? Q2. When the period of two years of advance maintenance start for building / flat owner - unilateral from OC received date i.e.May,2018 or majority possession date i.e. Sept.2018 to December 2018. Q.3 Under which law and sections this two questions fall for sake of clarity and for seeking legal remedy and redressal.:- Maharashtra Societies Act.1960, RERA, Maharashtra Ownership Act,1963, Consumer Protection Act.or any other applicable law. Q. 4. Which Competent Authority to be approached for redress and in which court for filing case. Please help