A) That's not how hybridization works. In the vast majority of cases there is something called Haldane's rule: according to the rule the first generation hybrids will have sterile males and fertile females. After several generations of backcrossing fertile female hybrids with the maternal species fertile males will appear.
b)Species has no consistent definition. There are several alternate definitions and currently not a single one is absolute. However the general consensus is that species are a group of genetically identical organisms.