clay pipe

I scoped my sewer main. Started at my exterior clean out, about 10 feet up the line, just past a 90 I see something that looks like pipe separation... or possibly an old 2inch clay/castiron pipe converted into a 4 inch plastic pipe. This section of pipe has caused clogs and backups over the past...

I have had sewer gas leaking into my basement for a while now. I have narrowed it down to the laundry room where there is a 4" clay p trap in the concrete, drain on one side and a cleanout cover on the other. I think this is the culprit but not entirely sure. Also on the drain side is my...