My class took the RHS exam for NELDA certification and it had a lot of random facts. We used Dale foundation's RHS modules and practice exams. I would suggest you know every fact, because you never know what is going to be asked and we thought we were gonna fail during the exam haha. But due to the lenient grading system we all passed, so I think that if you know the main points, you should be good without know every little detail, but if you want to feel safe, I would recommend looking into the details. Good luck!