What is the ruling on taking an exam without having fully studied the curriculum, and sufficing with a general understanding or prior knowledge to answer the questions? Is this considered cheating or dishonesty?

A student should strive in their studies and recall what they are tasked with recalling. Answering from prior knowledge without studying, or from general understanding, is not cheating, but it exposes the student to the risk of error in their answer. It is better for them to diligently study and acquire knowledge.