How to determine maintenance to be collected by builder

Ours is an apartment complex (newly constructed in Hyderabad), The apartment is occupied since last 1.5 year. so far approx 40 flats occupied by the residents out of 112 flats. rest of the flats are not occupied so far. around 10 flats are still with the builder and 30 flats are with the landlord. few amenities are still pending to complete, like entrance, gates, goods lift etc. in spite of low occupancy we were paying the maintenance at agreed rate on psf basis to builder since last June, since we are getting uninterrupted utility supply, housekeeping, and lift, security etc. Note that these charges are paid by 40 flats only out of 112 till date. my question is what is the builder's role? is he not supposed to collect maintenance from all 112 flats, irrespective of occupancy? is it legal to collect maintenance dues without 90% occupancy?