Basement Rough-in

My house was built with a rough-in for a basement bath. There is a 2" PVC stub coming up from the concrete in the tub location and a 3 1/2" PVC stub in the WC location. In the lav location is a 2" PVC coming up from the floor with sani-tee and stub for the lav drain. It reduces to 1 1/2" above the sani-tee and continues up to connect with the laundry vent on the floor above. I want to believe everything under the slab is properly vented but hate to assume anything. Does this sound like a standard rough-in? Is there any way to verify the venting is correct?

Thanks.

You would want a 2" vent for the bathroom group going upstairs to revent on the next floor.

It may be that the 2" near the tub also is venting the toilet.

No way to tell without seeing HOW the piping was installed. There is little visual difference, above the floor, between a properly installed system and one which is completely improper.