Should an interviewer stick strictly to the questions he or she has generated before the interview? Why or why not?

What will be an ideal response?

It depends on the goal of the interview, but in general this would not be advised because it reduces the interviewer's ability to probe for additional information based on the interviewee's responses. The interviewer should remain flexible enough to ask additional questions and probe further, as needed, yet still ensure he or she asks all the vital questions needed to address the overall goals of the interview.