How to select all windows?

Well it is good that you are curious to know about such stuff, and using these shortcuts definitely saves time and are really important to know, so I am giving you list of few useful shortcuts that could make your work easier and simpler.

CTRL + A (SELECT ALL ITEMS)

CTRL+ C (Copy)

CTRL+ X (Cut)

CTRL+ V (Paste)

CTRL+ Z (Undo)

DELETE (Delete)

SHIFT+ DELETE (Deletes the item permanently without sending it into the Recycle Bin)

F2 key (Rename the selected item)

F3 key (Search for a file or a folder)

ALT+ ENTER (display the properties of item)

ALT+ F4 (Close the current window or program)

ALT+ TAB (Switch between the open application)

F5 key (refresh the active window)

CTRL+ SHIFT+ ESC (Opens Task Manager).

Hope this helps you out.