4. what is the simplest way to permanently get rid of an unwanted file?

It depends, if it's chromebook, go to files and click the file or folder you want to delete. Click Delete to Delete. You can also use the shortcut Alt + Backspace. For Apple, Drag the item/file to the Trash. Or click on the item, then press Command-Delete. Click the Trash, then click Empty. When you see a warning message, click OK.

Ihave never used that feature before but i think it's true