Wow, talk about a deep subject, (good one).
1. when you are hybridizing any plant, if you continually "Line Pollinate" then at some point you would have some of the seed revert to the original color, not all would do this but there would be some.
2. Seed houses use green houses and all species are kept separate, pollen is collected and manually applied to get seeds of the genetics desired by the grower, all pollinated flowers are encased (usually with a glassine paper cone that can be closed off) after the pollen is applied so that no stray pollen has a chance of contaminating.
3. when it comes to flowers the seed genetics will match the flower attributes, if they didn't you would not have that particular flower coloring.
4. yes they will cross pollinate unless you segregate them some how.
5. the plant is an annual and its genetic make up doesn't make it able to overwinter. I am sure you could have success but the equipment would probably be quite expensive and then there is the space requirement for the equipment.
(Get yourself a copy of this book (or something very similar))
Flower Breeding Genetics, going into such a project with out knowledge almost ensures failure at least at first.
Redhawk