so i watched this video of someone running cod 4 an made me want to learn to run cod 4 in some missions like crew expandable he was able to walk through certain doors like the manifest container before it was actually open and skipped the whole part where the ship blows up an you have to get back to extraction, when i checked on here i saw a guide for each level with a video attached an none of that happened on the tutorials here, i know that if you run a level fast enough some buggy stuff can happen. just not confused as to why it never happened in the tutorial video on here.

Video you sent features a Speedrun Mod, something that changes the game removing certain waiting sections and RNG to make the run more enjoyable. The runs for this mod have their own src page. If you are interested, check it out. https://www.speedrun.com/cod4sr