Generally speaking, this problem is very complicated, big and important, or there are newly discovered problems. The bigger one can be called the "main body".
Papers can be written by many people together or by one person.
Generally, bachelor's degree, master's degree and doctor's degree can only be obtained through thesis defense, that is, the tutor will ask you some questions about your thesis, please answer them, and see whether you are qualified to obtain a degree according to your answers and the situation of your thesis. You know, you have to use mine ~