I don't know the breeding conditions. I can answer your second question. Yes it is possible that's why colors in the two species are so similar. The offspring are mostly sterile. Mollies and guppies can also crossbreed.
A good ratio for live bearers is 1 male/two females. So providing 2 females for each male will keep them pretty well peaceful.
Temps of about 78-80F, good food and clean water are important in breeding live bearers. They will carry their babies for 28-30days and can have 3-4 batches of babies from one mating because the females store sperm.