Student or Learner
If any of my interpretations is wrong, please correct me.
1. Is she a teacher? - I wonder if she is a teacher, I'm not sure she is, I'm more negative about her being a teacher.
2. Isn't she a teacher? - I'm kind of sure of believe she is a teacher, but I'm not sure.
3. Is not she a teacher? - unlikely to be said. Do you ever say like this?
4. Is she not a teacher? - I'm surprised to know she is not a teacher.
Can you explain why 3 doesn't work? I think there's no reason, they just don't say it.
3. Is not she a teacher? - Wrong.
But the 'Is not she...' version is occasionally used in rhetoric 'Comrades, is not this the point of no return?'; but even then, it's rather dated. In Jane Austen I wouldn't be surprised to see 'Is not she "the belle of the ball"'.