Clarification on occupation certificate from builder

Hello, I have bought an independent house in a gutted community last year which have 200 units.Around 80 units are occupied as of now.We have occupied the house 8 months back. I have few below questions. Could you please help?1. Some of the works are not done and the quality of painting is also not good. I have been chasing them from last 8 months but no use. Is there anything I can do here for those few works?2. Builder took amenities amount from only few owners as on date. I am among them. Most of the people who have occupied even before have not yet paid. It’s already 8 months that I have paid.But amenities are not yet complete and may take another year. Generally when we have to pay for amenities and how much time a builder can take.3. Regarding OC, When I asked builder he said it will be given only after all the project completes and it may take another year or even more. But already 80 units are occupied. Does occupation can be done before OC and can he collect maintenance