I'm a pretty lazy cook, so often when I buy stuff, it can be several weeks before I get around to cooking it. If I buy a bag of potatoes, they can remain in the bag on the veg rack until I notice that they're well into sprouting (having used chips or powdered mash in the meantime). I've always laboriously snapped off all the sprouts before cooking the potatoes, but I wonder - is it necessary for me to do that, or are the sprouts edible without ill effect?
No, you shouldnt plant them. You should only really use seed potatoes for growing a potato crop. If you plant non-seeds, you may be encouraging disease.
Not if you plant them in a container, barmaid. I've also had potatoes off my allotment that were perfectly alright when I missed some from the previous years crop.
They start sprouting within days of purchase. I regret the nutrition loss but that's the usual state I eat them. As for leaving on the shoots, doesn't appeal to me, but my pure guess would be that they were edible. Try them and if you are still around tomorrow, let us know.
Kept in the fridge potatoes last longer. If they sprout just remove the sprouty bits when you peel the spud.... continue as normal. They are fine but peel any green flesh off when you prepare them. I keep almost all veg in the fridge and they last for a long time. Waste not want not!!