Level one has the cart secret that lets you skip finding gas cans.

I went that way. In Chapter 2 at the end of a long locker room there is a keycard.
Then if you go left in the large room after that, you can use the card.
For me, it is glitched I think. The door opens but the caution sign stays there and we can't move past it.

If you want a meta backrooms themed shortcut, literally just turn on NoClip and go wild LOL

Jokes aside, in level one I found out you can not only do the Peanut shooting gallery but has also a bunch of optional ways of finishing that level, there are 3 so far that I found, one is the shooting gallery, the one is the plantation's gas station (search for a vent, you will need to break the wooden party thing blocking it) and the other one is the cart Tenebrae mentioned.

I made a separate post about this but when you find the executable, if you have the patience to look for it, no it's not a virus.

I know it's hard to trust a random fu_k from the internet but don't worry, you can run that with no problems, of course check it before running but go without worrying about it...I wasn't able to finish it yet tho so I cannot give a full opinion over it.

The executable has something to do with the projector on map_1 Party and it has nothing to do with Left 4 Dead 2's game, its a separate thing.