Did the Reptilians bring all or some of the reptile species to the earth and for what purpose? Did that include snakes, lizards, alligators, and crocodiles?

They did bring the toads, and multiple reptile species, including the snakes, the lizards, the alligators, and the crocodiles. There were variations of these in prior epochs on the earth, as species are often introduced in many worlds to provide many differing settings and to provide a backdrop for the plans for that location. Some are testing ground, some are proving grounds, some are simply there to provide variety and opportunities for exploration, study, and interaction with more advanced beings, who may visit and do work for a time in other worlds and their environment, and gain knowledge. So, as you know, many species in the fossil record on earth are no longer present on the planet and that is true of the reptilian species of old. The newer variations were reintroduced by the Reptilian extraterrestrials because it is in keeping with their history and their culture, their normal environment, to have many such species to which they relate strongly by sharing some of the similarities innately. And so they have a bias favoring these organisms, much as you admire those animals that break into song like the birds, and those with beautiful plumage and behaviors that are endearing in some way to human sensibilities, particularly those that get along well with others and are not violent by nature. The opposite is the case of Reptilian encroachment. They have a predator mentality, and so the predatory species are interest to them and preferred by them because it is a reflection of their own nature and exalts them, in a way, in their thinking.