Undone vs Not done

Solution 1:

There is a difference between the past participle of "undo" and the adjective "undone". The OALD, as the Merriam-Webster dictionary does not take this meaning into account, but the SOED does (reversed, annuled).

(OALD undone adjective [not usually before noun]
1/ ​(especially of clothing) not fastened or tied
​2/ (especially of work) not finished
3/ ​(old use) (of a person) defeated and without any hope for the future

The SOED lists "undone" three times, two entries are adjectives and one is the past participle of "undo".

(SOED) undone a.¹ Not done, unaccomplished, uneffected, incomplete.

(SOED) undone a.² 1. Ruined, destroyed; reversed, annulled.
2 Unfastened, untied, loosened