This is important because this means you can not only re-plant the seeds from your harvest, but also have a legal framework and full permission to do so. Personally I never cared much for gardening, but the independence from big companies makes growing your own food much more attractive.
Yup, I do grow things from the supermarket all the time. It’s a myth, most things grow just fine. Sometimes they spray growth suppressors on things, like garlic, to prevent them from sprouting in transit, but otherwise it works fine every time.
As far as whether it’s legal or not, again, those cocksuckers can go get fucked. I’ll sell the shit too if I want to, it’s fucking mine.