Some topics are general and are regarded as 'classical' because they are always relevant across time periods through being relatable even as time progresses. For example, topics or themes about politics and satire would still prevail until now. Other topics or themes (such as viral videos) are only for that particular event and do not always occur, thus they do not prevail in the long run.
The suffix of encoded is "-ed" which shows that it is past tense.
The answer is "plentiful"
The speaker’s mental state shifts more and more toward madness.
This is because as the poem closes, the word nevermore occurs in more and more depressing situations because it is the only word the raven can say, and the poet asks him questions to which that can be the only answer. These questions become maddening and more depressing as time goes by.
