Undo on an iphone/Ipad in various applications (i.e. IOS Notes Undo, ...)

The Undo function is typically not in any menu in your iPhone applications... if it is not... shake the device... and you will get a pop-up menu (much like what you get when you select things)... Undo is one of them... in case of Notes: you get two UNDO steps... not a lot, but sometimes a lifesaver !

Unable to delete files (in Windows User Folder, in Downloads Folder, ...)