What is the criterion for cheating on exams, and is it permissible for teachers to provide students with exercises that are likely to appear on the exam, and what is the ruling on practicing previous exams for a teacher who will include some of them in his new exam?

Cheating in exams means that the student copies the answers to questions from a book or a classmate. This is a form of deception that defeats the purpose of the exam and contradicts trustworthiness. As for the teacher giving practice questions that may include exam questions, this is not cheating. One should be careful not to delve too deeply or be overly meticulous in questioning, as that is blameworthy and opens the door to waswasah (whispers/obsessive thoughts).