i like to say : when is the shop open? is it still open? Are they still working? no need for -ed and not even passive i think. ;)

Is it open right now - it seems correct. You certainly do not need "ed" in the end of "open" if you speak about stores.

What you wrote was already correct. Open does not have an "-ed" at the end, even though it is in the passive voice. Closed, however does. I guess in this case it is an exception, at least I have never heard or seen open in the passive form in this context.

mmm...I don't like those teachers who make you doubt....or worse, that don't know...but you'll be good with all the help you get inhere!! have a great day!

Maria, the questions u ask shows how nice you get to grips of the language. Good luck. ;)