Let's talk about the postgraduate entrance examination. The tutor will consider some factors. First of all, it's not your age, but why you didn't go to the undergraduate course until you were 22 years old, whether you took the college entrance examination for many years, and whether you are sick, which will affect your tutor's judgment. As long as you are admitted, it is no problem to go to school, but it does not rule out that some tutors will consider this factor. It doesn't matter whether you have a doctorate or not. There are many older people, and no one cares at all.
I hope I can help you!