Switching between windows of one application in multiple spaces
There is a shortcut to do this, though it doesn't cycle between windows; it only allows you to choose one. But it will switch to it regardless of which space it's on. It's a convenient way to access App Exposé for any app.

Press Cmd+Tab to open the application switcher. When the application whose window you seek is selected, press 1. You can then select a window by typing its title, or with the arrow keys.