Is it permissible to cheat in the fourth level of a university course after repenting from cheating in previous levels, given that the course is not needed, is difficult to retake, and is beyond comprehension, or should one abandon their studies?

Cheating is not permissible at any academic level, due to its prohibition. The advice is to strive and rely on oneself without cheating. If a student is not proficient in a scientific specialization, let him transfer to another specialization that he is capable of, and consult people of knowledge and advice.