Is there a biological age drawback for comparable academic experience in order to get permanent position?
Four years isn't very long, actually, so I doubt that there would be much of any effect. However, you can't rule out implicit bias of individuals independent of policies (or the lack) concerning age.
However, you will be judged on what you have done with your time. Changing fields is perfectly acceptable and people recognize that takes time. But the quality of your work and the recommendations of your professors will far outweigh any issues about age for most people. There is no accounting for jerks, of course.
But if people who have worked with you can honestly predict your future success, then you should be fine.