The Salary and other perks are decided through The President’s (Emoluments) and Pension Act, 1951. This act has been amended from time to time to review the salary. It is also used to fix the pension and other benefits of retired President.
It is needless to say that the income of the president is Tax free.
Since the President does not need to pay income tax he does not need to file IT Return.
So there is no point in sending RTI application.