Actually all day I'm just installing cosmetic mods, not sure what went wrong. Perhaps it went wrong when I was reinstalling UFO. I did uninstall Immersive armors before starting on a new game though because I've heard of the numerous bugs that it introduces during the Helgen sequence. Somehow, the issue got resolved. I typed tfc into the console right after the first Stormcloak soldier's head got chopped off, wait for a few seconds when I'm supposedly walking towards the chopping block, then type tfc back in. The sequence proceed normally afterwards. But like what bben46 has mentioned repeatedly in a lot of previous threads, start a game with 0 mods, save the game after you've reached into Helgen Keep. Only from then on it is safe to reinstall the mods. :dance: