I have purchased a Builder Floor in South Delhi, for which construction is complete and all floors a

I have purchased a Builder Floor in South Delhi, for which construction is complete and all floors are sold to new owners. In the Stilt Parking Area, The Property has a large room (was used to store construction material during construction) and servant quarters. The servant quarters are allocated to the floor owners. But the ownership rights of large room in the stilt parking is not mentioned in Sale Deed of mine or any of the floor owners. Said Large Room is mentioned in the Sale Deed as "Other's Room", and is locked on behest of Builder.

My question is - Is it legally possible for Builder to retain such portion in the property after selling all the floors and basement in the building? If possible legally, Will the Builder as owner of mentioned Room, also have share in the land underneath the property? How many independent owners are allowed in a property constructed over a 210 sq mt plot? Is there any limit to the number of owners who can be shareholder in the land underneath on a 210 sq mt plot?