I noticed the "Everything unlocked glitch" is no longer listed anywhere, yet people all over the internet seem to want to know it. So I'll quote the original post I made back then, but adapted to be normal English.
Start a New Game, watch the opening cutscene. Once Tenpenny takes you on a ride around LS, use the jetpack cheat. Continue to watch the opening cutscene all the way until the end, you'll die automatically and respawn at the hospital with all the interior markers unlocked.
The original topic is still here actually, if you want to see it and make me feel bad about myself.