It would be easy to tell if it is a real Bianchi frame, just look for a B in a circle on the seat stay caps, Bianchi stamped on the dropouts and a B on the DT/HT lug. Provided the decals are original the frame seems to be older than '85 because of the Piaggio decal, and the over the BB cable routing and nutted brake mounting would point to early '80s frame.

The parts post date the frame by about 20years and depending how much the seller wants for the bike it would be worth it for the parts, if you like them.

Not all Bianchis are Celeste even the "good" obes. Back in the '80 almost all Bianchis except the top of the line model usually came in two colors usually Celeste and something else. Before '88 with the eception of a few MTBs no Bianchi made in the orient came in Celeste (although the Professional model may be an exception).

I think I can actually see the B on the DT/HT lug so the question that remains is... was this an Italian built frame or a Orient built frame?