The acquisition of house is complete when the possession of the house was handed over to you in July 2010. Though the physical possession was taken over only in 2011, it may be construed that the house was vacant during the period from July 2010 to 2011.
The interest payable on your housing loan upto the date of possession will be allowed as a deduction u/s 24 of the Income Tax Act in 5 equal annual installments during the financial years 2010-11,2011-12,2012-13,2013-14 and 2014-15.
I am not sure whether you claimed the interest for the years 2010-11 to 2012-13 in your Income Tax returns. If you have not claimed, you cannot claim now, as you will not be able to file revised returns also. If you have not filed IT returns for these years, you cannot file them now, because the time for filing voluntary returns is over.
You can claim the interest only for the financial years 2013-14 and 2014-15 by filing returns. If you have already filed income tax return for the financial year 2013-14, you can file revised return before 31st March 2016 or the completion of your assessment. However, if you have filed return for the FY 2013-14 after the due date, you cannot file revised return.
You can claim interest whether the house is self occupied or let out.