undivided share of land in apartment- not properly apportioned in Tamilnadu?

The builder of the apartment planned for 8000 sq ft ,but built only 6000 sq ft plinth and apportioned the undivided share of land to the existing 6000 sqft and retained the uds relating to the unbuilt portion. namely 2000 sq ft ,now after 15yrs, the owners of the apartment needs to rebuild due to structural defects etc .do we need to take the permission of the promoter builder ,What are the legal provision applicable,to the builder and the apartment owners namely . Transfer of property act,wealth tax , income tax, gift tax , stamp duty , etc in case the apartment is rebuilt by the original promoter, or a new promoter.Can the apartment owners sue the builder under specific relief act for transferring the retained portion, for rectification of original sale deed which stands as the hurdle to independent redevelopment of the apartment by the apartment owners, what is the stamp duty applicable in this case of rectification of title deed