Submit only one piece at time. We will respond to it as quickly as we can, and as soon as we do, you’re free to submit again. Unless submissions are closed. Closed off to you like so many of the better things in life -- is what I'd say if I were some blue-blooded aristocrat getting my jollies by ragging on the hoi polloi.
Yes, you can submit your work here and elsewhere simultaneously, but please let us know your work has then been accepted for publication as soon as possible. We'd do the same for you, possibly -- one is free to speculate, though.
No previously published work, thank you.