Professor Layton here's the only character I have.

1. Can Kari recognize your character? Yep.
2. Is your character's canon relatively similar or radically different in her world? Don't mind either way. Whatever's more fun for you!
3. Can Kari mention this to your character? Yep! Though he will probably just think she's cray.
4. Can Kari "spoil" your character? Sure thing. It can be as out of town as what pleases you.
5. Will your character recognize Hoshikyo? Not in the least.