Tax exemption on home loan interest if possesion is in the middle of a year

Hi, I booked an apartment and took a loan in May 2015. I got the possession of the apartment on 6th January 2017. Registration will be on 14th March 2017. Few questions: 1. For income tax deduction on home loan interest, under section 24, can I claim exemption from the beginning of the financial year or from the date of possession or from the date of registration. 2. Under which section can I add pre-emi interest. Thanks,