I don't install the trap until I know for sure where the drain is located. Owner may want a 36x36, 36x48 or just a tub. Each requires a different trap locationI think Larry is correct. Keep digging a little more and you should find the top of a pea trap. Not sure why they didn't leave a piece of pipe sticking up.
Seems like a shower drain and it's matching vent. Why it's not over by the toilet and sink makes no sense.
I suppose that would be fine- it's horizontal wet venting. In the OP it's an individual vent at the T/S and judging by the other vents it is plumbed correctly but much different that you image. Both are code approved (different codes have exceptions for horz venting. UPC vs IPC)
It looks like most of the drain and venting is installed and connected. You need water piping, fixtures and walls of course. The waste & vent is the most difficult.Sorry I didn't get that in the picture. The left side of the wye goes up to another bathroom sink on the main level.
I saw the kitchen line in a previous picture. It wyes into the 2" vertical line below the lav- totally legal. See post 23Now I'm just more confused.
Pipes on the right mostly make sense. Pipe on the left you said the kitchen sink ties into the same line that it ties into.
You had a picture of a wye (tie in) under the slab. Is that where the kitchen sink ties into?
I would not think so and presume you got mixed up.....could be me though! 🤨