1. That has to be Harry, he always comes at 10 am. → Correct.
2. I might not to come to the club tomorrow because I have to go to the doctor. → I might not come to the club tomorrow because I have to go to the doctor.
3. I don't think we should buy him this tie. He mustn't like the color. → I don't think we should buy him this tie. He might not like the color.
4. This information must to be useful. → This information must be useful.
5. My brother have to walk the dog. It is his chore. → My brother has to walk the dog. It is his chore.
6. Have your parents to check your homework diary? → Have your parents checked your homework diary?