1. Am I holding a Government lease while owning a flat in a multi-storey building?

Yes. As an owner of an individual unit (flat) in a multi-storey building, you and all other owners of the same building hold the Government lease of the land on which the building has been constructed.  In other words, you are a co-owner of the Government lease and you are holding a portion of shares in the land. You have the exclusive right of possession of your individual unit and share the common parts of the building with other co-owners.