1. yea but its way way easy to test for allergens these days. if they somehow produced a cultivar that somehow produced an allergic reaction, it could be readily diagnosed. they used to, and may still do, those little tests, where they prick a kids back with needles containing all sorts of common allergens. i dont see how one could go unknown into the market.
allergens are legitimately super dangerous, and do require labeling. but never once heard of a food allergy specific to gmo crops.
2. way before GMO, you effectively could not save seeds. F1 hybrid cultivars are notoriously unstable, and the subsequent generations are almost always sterile or entirely different from the parents. its nothing new really.
yea they dont let you save seeds, but really, if we are being genuine and honest here, its intellectual property. in 20 years or w.e their patent runs out, im sure this trait will be all but free.