For Americans, we can exercise our options anytime from the moment we buy it, up to when the market closes on the expiration date.
If your option is In The Money (ITM), meaning the price you agreed to pay is under the market price, then I know on the last day before market closes Robinhood will try to automatically buy it for you as the option expires or they sell it for you if you don't have the funds to buy 100 shares.
If your option is Out of The Money, then it's worth $0. You can try to sell, but no one will buy because the price you agreed to in the option is higher than the market price.
The also if we open friday at lets say 18.00 and close friday at 15.00 ( hypothetical ) which price would take play.
The price that take play is the current market price at the time of exercise, regardless if you are the one exercising it or whatever broker you use.