I'd like to know how can one find the history of a deleted answer?
In particular, of this answer.
If the question was edited, there's a link to the revision history, just like there will be with undeleted answers. In this case, https://math.stackexchange.com/posts/1680571/revisions
And if it wasn't edited, then using
https://math.stackexchange.com/posts/<answer number here>/revisions will work just fine.
You can also access the timeline by replacing
timeline. So in your case, https://math.stackexchange.com/posts/1680571/timeline will work.