Hra & interest on housing

you can't claim the tax benefit of house loan until you get the possession of the house.  AFter you get the possession of the house you cna claim the pre-emi interest paid till the previous year relevant to the previous year in whihc you get the possession of the flat in 5 equal isntallments.  Also you will get benefit of teh interest paid for teh current year as well both upto 1.50lacs.

Yes after you get possession of the flat you can claim benefits both for house loan & HRA.  However for HRA you will ahve to prove that you are paying the rent.  For this you can preserve teh rent receipts.