This probably depends on the university. At mine, a faculty member may take a class (undergraduate or graduate) at a reduced price provided there is room, but enrolled students have priority. It is not common, however, to take advantage of this opportunity. Usually a professor prefers a more compressed and accelerated way to learn material that is spread out over a full academic term in an undergraduate course.

If professor didn't taught you even for once, you are in a horrible danger of taking educated people seriously

Yes they can

Of course, they can.
I was taught by more than 8 professors in my 100 and 200level. So many Doctors.lol

It is only in Nigeria that professor is not synonymous to a lecturer.

In the US, a professor is the lecturer, others are assistant. Whether undergraduate or graduate.

It is because we have few professors in Nigeria that why a masters degree holder will be lecturing.

Why not? It's just that some of them are too proud. If I were a Prof, students will enjoy me.

Yes, professors teach better than all those Lecturer 2 and Assistant Lecturers. In fact, they make the materials easier and they make you enjoy the course.

Microsoft10:
This probably depends on the university. At mine, a faculty member may take a class (undergraduate or graduate) at a reduced price provided there is room, but enrolled students have priority. It is not common, however, to take advantage of this opportunity. Usually a professor prefers a more compressed and accelerated way to learn material that is spread out over a full academic term in an undergraduate course.

Sure, they take undergraduate classes. During my days in the University, different profs taught me at different levels upto 500L. (100L inclusive)

But majority of the lecturers that taught me were PhD holders though. The best of them were still those profs