1. How do you get a red-spiked Shadow chao?

You have to breed chaos to do that. First you need to have at an adult Red chao(or shiny red, but regular red would be easier) and preferably an adult ordinary(not rare kinds if possible) chao and mate them.

You can force this by feeding chao heart fruit to both chaos close to the same time. Let the first chao go into "flowers" then as soon as the second chao is finished eating, imediately pick the 2nd chao up before it goes into "flowers".

Make th 2nd chao face the other one and they will mate. If the baby is a red hybrid chao ( an ordinary chao except it has a thin overcoat of a rare color, in this case red.), raise it to be a dark running chao(pet it by a dark character a lot and give it green viles and/or running animals), and when the chao becomes an adult, the red color will replace that green color for normal dark and running chaos.

I myself have a chao like that named Shadow3.