The free version has 16 dates per boy, the full version has 20 dates per boy. Sometimes a guy just won't go to a location more than once and some spots they won't visit at all. That's why not all the date spots have the same amount.
The three heart bar is the final affection bar there is. If you've maxed that out than the guy likes you as much as he possibly can.
I hope that clears things up!