There is no self-taught professional examination for CET-4 and CET-6. That's for college students. Students majoring in self-taught exams can only take the exams of College English (1) and College English (2). However, after graduation, you can apply for graduate students enrolled nationwide. It is ok for self-taught students to take the computer grade certificate.

For other professional certificates, please refer to "China Education Examination Network".

Good luck!