Huge plot hole
1. I mean Kevin was 9 when he was 10 in the second Home Alone. So how can he be 10 and then be 9 again?
2. Kevin wasn't truly home alone.
3. Even though Kevin's character (even if they had used a different actor) wasn't in Home Alone 3, supposedly quite a few years passed, so that means that Kevin even if he were played by a different actor, he would be too old to be home alone. Because supposedly quite a few years have passed.