First, in your example, there is nothing preventing your competitors from searching for your first "lost" golf ball within the alloted 5 minutes (you cannot tell them to ignore your first lost golf ball or tell them to not look for it). If they do find it, you must play it as it lies, assuming that it was not hit OB. a). I believe that is correct. b) Correct. c) Correct. d) Correct. e) Incorrect. As soon as you play additional strokes with the provisional ball, your original ball is deemed removed from play. In this example, you have 5 minutes to walk forward of your provisional ball's position to find your original ball.
I actually believe e) is correct. From my understanding (I could be wrong), but you can continue to make strokes on your provisional so long as you haven't reached the point where the original is. Rule 27b: The player may play a provisional ball until he reaches the place where the original ball is likely to be. If he makes a stroke with the provisional ball from the place where the original ball is likely to be or from a point nearer the hole than that place, the original ball is lost and the provisional ball becomes the ball in playunder penalty of stroke and distance (Rule 27-1).