What to do with these onion plants?

Hi I am not sure what to do with some onion plants and need advice from experienced growers.
I bought a big bag of yellow onions and some started to sprout before I can use them up. I planted the sprouted ones over a period of 4 -6 weeks in late winter this year. In early summer some bolted and the rest keep growing and dividing. Apparently the day length and temperature combo is not favorable for bulb formation.  Now I have several clumps of lush onion greens 2.5 ft tall. Here are my questions:

1. I have 4-6 wreks of frost free days left, will those still form onion set somehow?
2. Will they get winter killed above ground and regrow next year or they are not hardy at all?

I am not sure of the exact variety, but if they can't grow bulbs I might just use them as bunching onions now. Thanks.

Your onions likely didn’t form bulbs because they aren’t the right day length cultivars for your area.  Onions come in long, intermediate, and short day cultivars, based on the length of your summer days.  Onions form bulbs in the late spring to early summer in response to the lengthening day length and often go dormant for part of the summer, so your onions won’t be forming bulbs this time of year.  Onions are cool season vegetable and are very cold hardy, but will need to be mulched if you are expecting extended below 0F cold snaps.  

Are they potato onions? They look like they have divided into many smaller bulbs,keep watching them,they might get bulbs on in the shorter days.They will most likely winter over if your temps are not extremely cold,after they die back some cover them with a heavy layer of leaves or straw and see how the do.They may just bolt come spring though since they are a biannual plant.You could just eat them,onion soup onion stew,onion sandwich,fried onion,boiled onion,yeah not that last one.

They are regular grocery store sweet onions with yellow skins. Each clump is from a single sprout since I carefully cut the onion open to get 2-3 plantlets. Since it divided into a big cluster, I guess I will need to separate them and replant next spring? The base seems to to filling out a bit I will keep watching.