Tamilnadu Forming apartment owners association

Hi Ours is a gated community in Chennai comprising over 500+ apartments. The builder is yet to complete the project and partial handover is done and currently approx 174 owners are residing after taking possession. My query is can we register our Association prior to project completion and possession of all apartments? The builder is insisting to form the association as there are about 30% occupation..I'm suspicious of the builders motive as the project completion is already delayed by over 4 years and fear if an association is formed he may delay completion and handover of the remaining apartments and amenities such as Clubhouse..Water treatment..STP etc. Pls guide me as appropriate. Thanks