Show all windows on hover/click doc icon (Mac Yosemite 10.10.5)
Solution 1:
Double tap (not click) the open application icon. This will display all open windows for that application and you can select the one you need.
If you are using a non-Apple mouse/trackpad you can right click or two-finger click an open application icon to reveal a list. The top entries are the open windows for that application. You can then select one of the open windows from that list.
Solution 2:
Using two fingers, tap (tap not click) on twice to the application icon in the dock.
Solution 3:
Alternative to existing solution, which is right clicking on the app icon in the Dock and clicking on the desired window:
Enable Exposé in System Preferences > Trackpad > App Exposé (for trackpad shortcut) or System Preferences > Mission Control > Application windows (for keyboard shortcut).
Then use your Exposé shortcut to show all the open windows for your current application. This will not show full screen windows. To see other applications' windows click that application's icons in the dock while in Exposé mode.
Then click the window you want to give it focus.
Exposé includes windows on other desktops and minimized windows.