Firefox – How to save/export Firefox search engines

Shift-Delete is the key combination to do this, however it's not the "delete" key you'll find on a macbook keyboard. On a MacBook or other Apple keyboard, you should use Shift+Fn+Delete.

On a windows keyboard, the key in the top right corner of the main part of the keyboard (two rows above the enter/return key) is labeled "Backspace". There's a separate key labeled "Delete" to the right of that, grouped with Page Up/PageDown, Home and End. If you have an external keyboard with this layout, use that "Delete" key with Shift.

Yes, in general you should be able to use a shadow copy to "go back in time". Just make sure you restore the whole folder.

Extra note: Use a tool such as Malwarebytes.org to ensure everything is indeed removed (some components might hide in background or be loaded by other processes, e.g. those using Internet Explorer, in case you only cleaned Firefox.