I want to add a basement toilet, can anyone tell me is this plumbing is adequate? I would like to use the clean out at the bottom of the plumbing. I s this plumbing adequate for venting? See attached photos.

Great shots of your PVC drainage but it's what's under the slab that interests me. You will have to freak up the floor and locate the main. Once located you will need to cut a wye in to pick up the toilet. But why stop there. Since everything's all tore up why mot install a bath group, (see image). You will have to run a vent up and revent back in the attic if you don't want another hole in your roof, Good luck, Tom