UCC25600: What are the problem of TL431 loop compensation and R17 and C23, respectively?

Question 1

What is the relationship between the switching frequency of the half bridge converter and all the zero and pole points of the type III loop compensator?

Question 2

What role do R17 and C23 play?What is the basis for the C23 value?

                                 Figure 1

My personal understanding is that the switching frequency of a half bridge converter is lower than the frequency of all zeros and poles? Is this idea correct? Thank you!