Replying to Nigrescence comment, the game takes the outputs of the first time you beat it even if you delete the save files.
Also, the fact you have to delete your data for all the achievements is very awkward, but even with that in mind, remember this is still a game and it's especially focused on making your own choices. Why would you encourage people to play this with the guide in hand from the get go, especially when for the most part it doesn't have a right answer for their problems.
If you don't see fun in the concept without achievements then you're simply wasting your time, and that's not "happy", even for a completionist

Do you need to complete all under track missions for the True Utilitarian or only the missions where you have a lever to pull?

Yes all of them need to be completed with the exception of Trolley-o-poly which you can exit and the next stage will appear. Just updated the guide with this info.

Pro Tip for completionists: Do "True Deontologist" first, then "True Utilitarian", and then you can complete everything else.
I played through normally first before deciding I wanted to complete all achievements. Don't make my mistake, I have to play through all the sub-stages again. Take my advice and you'll be happy. For full completionism, you can even do the not-pulling of levers on every main stage afterwards just to turn the flags fully black instead of half-and-half.

when you pull a lever in an above track level you'll need to complete the under track level in order to unlock the next above track level, so on and so forth

Do you need to complete all under track missions for the True Utilitarian or only the missions where you have a lever to pull?

There is no completion requirement for the DLC. Even for the True Utilitarian achievement, the game ignores that stage.

Thanks for the guide! It is possible to complete all the achievements without the dlc?

...the two "True" achievements are absolute madness...

Thanks for making a guide!