Ctrl+Alt+Backspace
You can configure a shortcut to do this yourself. Go to System -> Preferences -> Keyboard Shortcuts, and somewhere in the very long list will be something like "Maximise Window". Click the space next to that and press your shortcut, and you can then use that.
On PCs, it is ALT + F4. (caution, this will close the window ;) )
Windows logo key + E
I don't know about individual windows, but you can kill a process with killall. Please be very careful with this command, because it can damage your system.
Keyboard Shortcut
It is not clear what you mean by "tab," but if you are talking about a window, then there is no shortcut for Excel to minimize or maximize a window. You need to click on the symbols in the top right corner of the window to maximize or minimize.
There are many different ways to Undo in Photoshop. Ctrl + Z is keyboard shortcut for Undo last operation, Ctrl + Alt + Z is Undo keyboard shortcut. You can Undo and from Edit > Undo or from HISTORY panel (Window > History).
The keyboard shortcut function control-w or ctrl-w closes the window of the program you're in. It's the opposite of ctrl-n, which opens a new window.
ALT+F4. A lot of window managers and desktop environments on Linux also use this shortcut.
Why the window key in keyboard?
by double click shortcut on the desktop.
F1 (usually found in the top most row of the keyboard, towards the right of ESC button)