How can I politely reply and educate students with unreasonable requests?
Let's assume your teaching practices are the best possible.  Students want you to change your teaching practices.  You should respond by explaining to students why your practices are effective (do this even if they don't ask).  

Examples:


  additional exam papers with full solutions (there are already three
  past exam papers with solutions available).


Studying the three past exams will help you learn what you need to learn from this class.  Additional past exams will not provide additional help.  If you have extra time, I suggest you ...


  a list of the exact topics that will be examined in each of the exam
  exercises (this is, if the exam contains 5 questions, then I should
  provide the corresponding 5 topics).


All the topics listed on the course syllabus are important things for you to know.  Therefore, any of them might be on the exam and you should study all of them.  If it was not important enough to be on the exam, then I did not teach it.



If these types of responses are not true, then I suggest changing your teaching until they are true.