Construction of bachha flat in stilt parking

A builder has constructed fourth floor in delhi i.e. ug floor, 1st floor, 2nd floor and 3rd floor with roof right. In sale deed, he has provided/mentioned one car parking space to each of ibid floor owner i.e. car parking for 4 cars. He has no where mentioned in the sale deed regarding bachha flat constructed by him in stilt car parking. Now he is selling bachha flat. Kindly clarify the following in terms of law in subject matter:- 1. Whether the BACHHA FLOOR constructed by him in stilt parking is legal as per existing law or otherwise. 2. Whether he can sell the BACHHA Flat without consent of four floor owners. 3. Whether sale of bachha flat can be objected by the owner of all four floor, if so in which way. 4. If the construction of BACHHA FLAT is illegal, where complaint can be filed against the builder. 5. Also clarify whether any case can be filed against the builder for poor construction, if so where case is to be filed. 6. Also clarify the condition for any builder to build the floors and sale it i.e. qualification, engineering skil, registration for construction of building.