CE and PE rates are based on spot price or future price? Especially on expiry day.
CE an PE prices on your terminal are not based on anything but pure demand / supply and the same applies to Futures of the large number of bidders/sellers.
Just to set things straight
Now, Futures are "derived" from spot, but with Options, some Blackboxes and more recent articles tend to use the Futures price but the NSE tables use the Black-Scholes model and the NS as input.
The result is that the IV and other greeks etc may vary depending on the model.
Now again, from the above, there is nothing specific "to" expiry day.
Models that use spot will use spot, and Futures will use Futures. Models inherently cannot flip-flop
atleast, i never read of any.
*But on expiry day, not the weeklies, Futures and Spot prices tend to
converge and therefore it wouldn't make much diff in prices of both models but they can't switch the spot or the derivative.