Issue related to OC

I paid for an apartment in an Complex of 20 apartment in Hyderabad to a builder in advance when construction commenced, on completion of the apartment made the final on registration of the Sale deed and occupied the apartment even before the occupation certificate was issued by the HMDA relying on the builders integrity not knowing the legal implications. Also paid the 80 percent of the agreed maintenance charges to the builder. It is now 12 months passed, the builder has not obtained the OC. He is pleading delay due to lockdown. Over the last 4 months, occupants began to face maintenance issues in payment of electricity bill related to common facility, operation of water supply and lift and payment to care taker. To avoid breakdowns, 11 buyers occupying the apartment, assume responsibility to pool up the amount required for the monthly recurring expenses by mutual consent. Please advice on course of action on builder to obtain OC as he is indifferent in completing his responsibility to complete pending gworks, division and assignment of parking area, Registration of RWA and issue of OC.