Well we are getting a 4-star because I just had finished my 30th hour when I decided to do some miscellaneous quests when I realized I couldn't finish any of them because I technically already beat the quest out of sequence and it hardlocks future quests from being completed.
For example when joining the Companions of Whiterun, you have to take a quest to go defeat a bandit leader. If you so happened to come across him prior to the companion quest and kill him, you can no longer finish the quest given by the companions. You can't even resurrect him and finish the quest. Hardlockable game to the max. Also you can't sell the leather straps before giving the tell Alvord in Riverwood or you'll always be stuck with that quest too, you can only give him back the original leather.