1, b does not assume any responsibility, because he is only an intern, and he has no qualification and power to work independently, so his signature is invalid;

2, this matter should not affect B later, an intern will of course listen to the supervisor;

3.a should not have any purpose, but it is not appropriate for interns to do formal work.

I don't know what status you are as an intern. You can check the relevant internship regulations in your own internship unit.

For example, interns in hospitals have no right to prescribe drugs, and interns in banks have no right to handle business. Even in the enterprise, if something happens to the apprentice before he is full, the master will be responsible.