Where can I find historical options charts data specially for stocks options for backtesting?
Only current month, next month and far next month data and charts are available on Kite.
Where can I find expired months charts?
NSE provide paid historical data so far I know. But you can switch to OPSTRA for backtesting as you don’t get particular options backtesting feature from NSE but on the other side OPSTRA provide backtesting upto year 2019 options.