There are some basic fundamental disconnects with your hypothesis; A) If the lending rate is 8.50% p.a. then how will a deposit rate be 10% p.a. ? B) In a Cash down (ADF), generally developers will give a discount on the basic cost of approx. 6 to 8% -which has not been factored in cash flows. C) The difference between PRE EMII & EMI does no accrue in month 1 as you have shown in your illustrations. The gestation period is of 24 months as per your assumption and each month that difference accrues for the first 24 months.
Need less to say let us keep out the complexity of present/ future value etc away from the general public.
The best option is a Tranche EMI - do some research on the concept and interpolate it.
I think Home Loans are a complex financial tool which also has IT sops hence publishing articles which are incomplete like this one are misleading.
