Is it possible to reverse the likelihood of re-injury after a (2nd) grade 2 hamstring tear back to as it was before the injury?

Your muscle will never be the same as prior to your injury. But there is no reason with proper rehabilitation and continue to stretch and strengthen your muscles ,Not just the hamstring muscle. You can achieve improvement. The quadricep muscle is just as important. So all your muscles. You might be able to get it to 99% so do not give up. Remember you are still growing