1) My first question is about Fidya:-
Assume that I am liable to pay fidya for certain fasting days of Mahe Ramzan. I know that as per the law, for 1fast I am supposed to give 3/4 kg of wheat in the form of fidya. My question is that is wheat the only thing that can be given as fidya or I can give other things aslo such as milk, rice, salt, and other such things which may be useful to the receiver also? Please guide me answer & more knowledge if i missed any point. Thank you very much.

2)My second question is also about fidya:-
I am liable to play fidya for the fasts of Mahe Ramzan of the last 15years. So now when I decide to pay the fidya, how do i calculate the fidya? I mean, If the fidya is not given in the year in which I am liable to pay, then is it that more fidya or penalty gets added because i delay it to more than one year? I mean, am i liable to pay the fidya (in the same value for the fasts which were left 15 or 14 years back ) .What are the rulings? Thanks you very much.

1) As per the ruling either pay wheat or flour 3/4 kg for everyday
2) There is not any extra amount of fidya will apply it will be same as you mentioned you are liable for 15 years then you pay for the total period.