I am about ready to install the bathtub/shower in our basement. The drain is roughed in and was left covered in sand for me. I have exposed it and am guessing that I will need to dig down and add a trap to it before hooking up the tub.

My next question is about the shut off vaves for the toilet. Do I mount a board in the studs to support them? The plumbing system we have is a manifold system (pex).

I am about ready to install the bathtub/shower in our basement. The drain is roughed in and was left covered in sand for me. I have exposed it and am guessing that I will need to dig down and add a trap to it before hooking up the tub.
Yes,you will need to add a trap and a raiserto pick up the tub/shower.

My next question is about the shut off vaves for the toilet. Do I mount a board in the studs to support them? The plumbing system we have is a manifold system (pex).
Yes the stub-out should be backed. There will be a angle stop hanging on it that you don't want flapping in the breeze. Regards, tom