What is the ruling on studying and circulating past exam questions that are publicly available, or among a limited group of students, whether they were written down after the exam or photographed without the teacher's knowledge?

A student's viewing of exam questions after they have been distributed to students is not considered forbidden or cheating. It is common for students to inform one another about what was on the exam after it has concluded, and this is not considered cheating by teachers. Therefore, there is no harm in circulating these questions to benefit from them, as long as they were not leaked before the exam.