Tax Exemption for Joint Property

Although it may sound a silly problem to most of you but I have not been able to get a satisfactory answer from most of the online forumss.
Please Help me

Background :
My mother owns a flat in Delhi where we are living and she is the owner of the house with no Loans taken for this house in which we live.
I dont own any house anywhere in India other than the one discussed below

Me and my mother have booked a flat with a builder under the joint name which is under construction and will be possesed by us after 4 years. The payment is being made on construction link basis.
For the new flat we have a bank loan for which I and my mother are the applicant . The EMI have already started as bank has contributed towards the initial payment and some of builder installments
I want to know the tax exemption which :-
1. I can claim
2. Which my mother can claim considering she already owns a flat(in which we are residing)
3.Moreover if the EMI is paid only from my mother`s bank account and later she receives 50% of the EMI amount from me