No clue :( ==> tax exemption on loan from family

Hi ,

For the below query I'm getting different version & not sure whom to believe. Eagerly looking forward to some expert guidance.

I'm going to book a flat for me. Besides loaning from a bank, I'm also planning to loan a substantial amount from my father (Snior Citzn), which I'll pay him back over time.But I also want to pay him interest on the amount he lends. I came to know that this interest that I pay to my dad will be tax free (upto 1.5L) to me.

My queries here are :-

1. Is there an upper limit of interest rate that my father can accept.
   
   
2. If so, then what paper works do I need to produce as proof of interest paid to him for home loan.
   
   
3. Will the principal amount paid is also exempted under 80C.
   
   
4. Any other points that I must take care during this process.
   

Thanks for taking time to go thru this post.