It depends on how the Axanthic gene conflicts with the Spider gene when produced with a Pied. Axanthic Pieds are not all white except for the head, so there's a chance it would have less white in an Axanthic Spider Pied and more pattern on it's body.
It can not be guarenteed that the genes will look the same when combined.
True, but unlikely. Look at the Bumblebee (Pastel Spider) Pied...