Joint housing loan between sisters

* We are in process to buy an apartment in Bangalore(agreement amount paid) in joint name of my wife and her younger sister(unmarried) purely for the tax saving and investment purpose.
* After making the 20% of payment to builder, we came to know that as per bank rule Sisters cannot be co-applicant for Housing Loan. (This rule applies to all banks)
* Now the builder is saying that HDFC can provide housing loan jointly to my wife and her younger sister so that both can avail tax benefit, but the sale deed and rest of legal process would have only my wife's name included.

I called up HDFC loan dept but they are not sure about it.

Question is:
1. Is it possible to buy an apartment where sisters apply for joint loan and the property is registered in the name of only one of them?
2. Can both the applicants claim for tax benefit in such scenario?
3. Would there be any issue while selling this property before the closer of loan?

Any advice suggestion would really be very helpful.