Very Novice plumber here trying to figure out how to set up a full bath with my preplumbed basement. I have a few photos of the situation and willing to email them since I cannot figure how to attach photos in this text. So here goes:

1. I know where the toilet and shower will be. Toilet on 4inch stub and the shower drain will be over the peagravel filled square in the floor.

2. Regarding the two 2in lines that protrude through the cement floor and connect with each other in the joist and (I assume) exit to the roof for a vent. Now, looking at where the two 2inch lines are how do I go about determining which one I can use for the bathroom sink or does it matter. One is about 18 inches from the toilet stub to the left and the other is 15 inches to the right and 4 ft in front of the toilet stub.

3. If I use one of the two 2inch lines for the drainage of the sink(s) do I need to cut into either pipe and place my own T in there to run it to wherever my sink will be or how is that done.

4. ALso, the two copper lines coming out of the floor by the main water meter and shutoff. Is that how I hook up the water supply to the bath and if so , how does water flow through there if they are open right now without water flow.

Yes these questions may seem pretty simple but I have no knowledge of basement plumbing so any advice is welcomed and appreciated.