Hi I am looking for a few answers I can't seem 2 find in nfpa70, pleez help.

The NEC is not to be used as a design guide, I suspect that is why you are not finding answers to you questions.

Per Section 90.1 (C)-" This Code is not intended as a design specification or as an instruction manual for untrained persons".

Sch 40 PVC is allowed as a riser providing is attached and supported properly to the building. Any aerial line will be attached to the building separately.

If by riser you mean a mast, a conduit that rises above the roofline for the purpose of attaching and supporting an aerial line, only steel conduit is allowed.