CUA is a union of Mac like mnemonic command keys on Ctrl plus another set (from IBM/Motif perhaps) that use shift+insert,delete etc.

Alt+F4 through Alt+F9 are for Window Menu operations, like minimize, max. etc. Some besides Alt+F4:Close still work on older window managers, I remember SGI supported all of them.

Newer ones tend to hide or even disable the whole menu! Even Windows as it is further lobotomized.