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.
First, let’s offer a bit of sympathy where it’s due: students are a population that’s suffering right now in some unique ways due to the pandemic. Being a student can be very stressful at the best of times, and my impression is that for a lot of them it’s now more stressful and challenging than ever before. So my first recommendation is to try to be less judgmental. What may seem like an unreasonable request to you may simply be a student’s way of coping with the extreme situation they are finding themselves in, seeking creative solutions, and asking for help when they recognize they need it.
The right mindset for addressing these requests should therefore not be about “educating” the students and showing them the error of their ways, in my opinion. Students have enough normal stuff on their plate right now, they don’t need to be lectured on the reasonableness or unreasonableness of their requests. Frankly, I think at the moment you should stick to teaching the material, handling whatever course logistics there are to handle, and being as accepting and kind to the students as possible. Whatever “educational” energy you have should be directed towards the course material rather than on imparting life wisdom. You’ll have plenty of time to help them with that when the world goes back to a more normal state.
So basically @JeffE and @cag51 have it right. If the request is unreasonable, just say no and try to do it in an empathetic way. Elaborate explanations are not really needed. But sympathy, and a sense that you understand what they may be going through at this difficult time, are.
I agree with JeffE's comment: just say no. Students already know why these requests would normally be unreasonable, they just need you to explain that these norms haven't changed. So, taking your first example, I would reply as follows:
Hi Name,
No, I will not be providing more than the three that are already available. While I empathize that the public health crisis has produced an unfamiliar and stressful situation, I believe three practice exams is already a very reasonable number.
With kind regards,