Both sentences about tests are correct. The 'the' is optional. Only 'have' is correct.

At the end of the fall come the hard tests. This feels awkward. The hard tests come at the end of the fall. Yes, but 'the fall' is just 'fall' = The hard tests come at the end of fall. Many hours at the driving range ✖has/✔have led us to .... Yes, the correct answer is have, because 'many hours' is plural. "Has led" and "have led" are both in the present perfect tense. "Has led" is used in the third-person singular and "have led" is used for first- and second-person singular and all plural uses. The present perfect tense refers to an action that began at some time in the past and is still in progress. For example, if I started studying art when I was 13 years old it has made me a professional, I would say "Many years of studying art have led me to become skilful and proficient in this field." However, most people don't know the difference between 'has led' and 'have led' in this situation. So feel free to use them both interchangeably.

At the end of the fall come the hard tests. Sounds odd and old fashioned but I think it is still grammatically correct. The hard tests come at the end of the fall. This is grammatically correct and conveys the same idea as the first. Many hours at the driving range ✖has/✔have led us to .... Both would be correct