D.K.
Many kids don't get that they need to stop playing to go to the bathroom. And they leave it until - oops - they just won't make it. We trained my son at 25 months. It took under a week until he was 99% there. But if he was having too much fun, and no one reminded him to go, he would leak a little, run to the bathroom and not quite make it. There is nothing wrong with telling him 'it's time to go to the bathroom' and taking him. We did not ask DS, we told him (if we asked, he never had to go). And of course, playing is way more fun than stopping to use the potty. I see no reason for you to go back to diapers or anything like that. I would give up the rewards. And I would not expect him to go on his own without telling you for a while.