Switching to an old model hybrid is a bad idea. Specially for fuel saving reasons because you won’t save anything, rather will spend a lot more on it.
Why?
You cannot buy a good condition hybrid/Prius in 36 lakh.
It will be very old, used and abused (2007-2012 max). It will have a dying battery and ABS unit (likely already replaced with used units) and it will fail again in some time.
Suppose even if you manage to buy an ancient Prius in 36 lakh, will have to spend 3-5 lakh repeatedly on its maintenance and fixing its parts/ABS/batteries.
Any fuel savings you make will be offset by the high buying price and extra expenses on replacing its failing parts.
Anything older than a 2018-19 Prius will have its parts failing. And you cannot buy a 2015-2019 Prius in 36 lakhs at all.
Older models will give you lots of trouble. Not only for Prius but other hybrids too.