Just in case a few of my fellow Douligians have not noticed yet, the suffix "-lich" is very much the same as the suffix "-ly" in english. You will see this pattern through out this lesson.
Du hast recht. Except in certain cases such as "selbstverständlich." Endlich = finally Wirklich=really etc. Aber selbstverständlich=? This one is an adjective, whereas "-ly" is a standard adverb ending.
Why would "kürzlich nicht" be correct, but not "plötzlich nicht"? They look as if they have the identical form, just different adjectives. (There were three selections offered, and the task was to select ALL that were correct.)
I translated "Nicht zuletzt" is it wrong? sometimes Duolingo isn't so helpful