Your 2nd ball, without the declaration of it being a provisional, is not a ball in play under the Rules. Technically, it would not count as a stroke at all and you'd either have to walk back to the tee and declare that you were hitting a provisional ball under stroke and distance (your 3rd stroke) or take a 2 stroke penalty and drop a ball in play near where you thought your original ball was (lying 3, hitting 4).
I do not believe this is correct. I think that if you do not declare the second ball as provisional that it (the second ball) IS the ball in play and all other options are off the table.
This is correct. If you hit a second ball and do not call a provisional, you've possibly screwed yourself 2 strokes.