There are two options available to you:

1. If there are already G+2 floors in the exiting property, then you can enter into a sale deed with your father before the demolition of the house and you can get the 2 floors registered in your name and your brothers name. Thereafter you can enter into a sale deed with your brother for the transfer of his floor in your name. Thereafter you can demolish and reconstruct the property. You can also transfer the shop in his name once the floor is registered in your name.

2. If there aren't G+2 floors in the property, then you will have to enter into a Memorandum of Understanding (MOU) or an agreement to sell with future consideration.

The MOU can contain provisions with respect to the transfer of the ownership of shop being subject to transfer of the title to the floor belonging to your brother. This MOU should be signed in the presence of witnesses and get it registered .

OR Indian Contract Law recognises three types of consideration: past, present and future. In your case the consideration is in future. So you can enter into a contract with your brother stipulating that he shall be registering/transferring the said property post construction in your name on or before a fixed date in consideration of your shop which you shall be transferring in his name post the registration/transfer of the said floor in your name. By providing such clear terms in your contract, if he does not perform his part of the contract before the date as mentioned in the contract, you can proceed against him for specific performance of the contract.

No registry of the floors cannot be done before they are constructed.