Builder overseeing maintenance for last 3 years. forcing us to pay maintenance charges

Dear Sir, Land owner and property developer entered into a Joint venture in 2015 to construct 8 apartments with covered car parking facility. 2 flats are occupied by the developer himself and 2 flats have been sold out to external parties. Four legal heirs of the land owner got one flat each. Along with JV, the land owners have signed an agreement with the developer entitling him to oversee maintenance until the welfare association is formed. The builder has not collected any lump sum towards maintenance as they do in other new purchases. They also agreed to pay the corpus fund at the time of formation of association. The builder has charged Rs. 3800 towards maintenance and GST which in total was Rs. 4661. per month. Realizing the charges were very high for the services provided, the owners met the developer in 2017 requesting him to cut down cost by removing un-wanted services like apartment security 24/7. But the developer did not oblige to it. The developer kept on adding to pending maintenance balance. three heirs of land owner has never paid any maintenance to the builder so far. One has let his property on rent. so the organization renting the apartment is paying maintenance on his behalf. the other one of the two external parties who purchased the house from developer are paying maintenance without any choice. the other external party has defaulted on his loan and bank has taken over his property. so no maintenance from him. we purchased one flat from one of the heirs of the land owner in December 2019. we have not signed any papers with the developer agreeing to the maintenance charged by him. we have not paid any maintenance so far. The apartment security and the builder has caused hindrance to us by locking the common door and roof doors saying security reasons. Every time we want to go out we need to get permission kind of from security to get the keys. The keys are with the builder and security guard. we also raised a police complaint regarding this. The facilities are favoring the builder and we don't want to pay maintenance for it. Now two heirs of the land owner and we have received a notice from the developer citing the non receipt of maintenance demanding the pending balances. Questions : 1. Legally, Is the developer entitled to hold the maintenance for more than a year or in this case until the association is formed. 2. Is there an option to force the developer stop maintaining the apartment immediately and work on formation of association when required. 3. Is is mandatory for an apartment with 8 units to have an association. 4. Can the developer take legal action on us for non payment of maintenance dues. If so what is the maximum action he can take. 5. under which court will these cases be heard. Civil or Criminal. and how long will it take to settle.