in example 6 Agne, how would we close the deal if we decide to not exercise the option since here we are selling and buying on the same date i.e 18th of September
The option is the tight to buy and sell futures on the date of the transaction. If they decided not to exercise the option then there would be no futures deal. They would simply borrow (or invest) the money at whatever the interest rate happened to be on that date(but, of course, would still have had the cost of buying the option).