Everything is childish with Michael. It's just that certain behaviors are far less charming or forgiveable when you're an adult than when you're a kid.
No, not at all. They can't learn to get better. At best they could develop some sort of symbolic shorthand for some vocabulary, but grammar in general is difficult for them.
Also, i love how you've shown his slightly more playful/cildish side, despite what he is xD x