macOs knows both behaviors: yellow button for "minimize" and red button for "minimize". If you open Safari for example and then minimize it with the red button, macOS will close the window, but not terminate the app! Click the red button again and macOs will "restore" (open) instantly a (new) window again but not the old session. That's what I meant.
What do you mean, restore with the red button? There is no red button if the window is minimized or if the interface is closed. There is just an image in the dock. If you click the image in the dock, you get back the window.
@concretable The precise point here is that if you click the image in the dock, you DON'T get the window back. If you close all your windows with the red button, you have to either do "file-new window/tab" or "cmd-n" to get a new window to open. The icon in the dock does nothing (unless you quit Opera completely and start again). That's the issue we're talking about.