What? Yes they do. They look for the chemical itself or its metabolites. Getting a sample sent off to a lab usually means "give this to a facility that can perform a GC/MS or whatnot and has enough reference samples on hand to determine what is in this fluid"
It depends. Floyd Landis was pinched by a test performed on a mass spectrometer !
Maybe. Part of the reason that he contested it for so long was that although he had doped he had not actually taken anything that would produce the reported result.