There are several missable friends, weapons/equipment and Chinpokomon that you can miss during your playthrough. If you miss any one of these things, you will have to start a new game from the very beginning (unless you created a manual save that you can revert to). Watch the video embedded above for a complete guide on how to avoid missing them.
Once you have got all the collectibles that are missable, you are freely able to get any of the rest at any time, even during post game free roam. Use the videos below for help in finding all equipment, friends and chinpokomon. For all other Stick of Truth trophies, visit this POST