Our flat scheme is around 20 years old, and we are thinking of handing it over to to some builder?

Our flat scheme is around 20 years old, and we are thinking of handing it over to to some builder for renovation. We do not have a registered society. Actually we are a part of registered society made by the builder with other schemes of him which physically does not exist today. Is it a fact that we do not have legal right to hand over the flat scheme if the society is not registered. If yes how can we register the flat owners society ?