[jbeam]

--Stock options are standardized contracts so it doesn't need to be the same buyer.

--Call options cannot be exercised (this would be requesting the shares) until the stock price exceeds the strike price. American options can be exercised at any time, European options can only be exercised at expiry.

--It's typically better to sell an American option rather than exercise early. Options have "intrinsic" and "extrinsic" value. The intrinsic value is what you get when you exercise. Simplifying a bit of messiness away, if your strike price is $30 and the stock is at $50 then by exercising and selling the shares you net $20. But the option at the same time will sell for more than $20. Thus by exercising early, you leave extrinsic value on the table. The time-to-expiry aspect is a significant portion of an option's extrinsic value.