Answer by Candace Vianna:
No, to the first part. These are not interchangeable. They are antonyms. Literally means without interpretation or embellishment, exactly as stated.
Figuratively means you’re not being literal, you’re using figures of speech or are speaking metaphorically.
The second part of the question is more difficult to pin down. Language evolves with usage. If enough people adopt a specific usage, then eventually that usage is considered correct. A prime example of this would be the word “disrespect. It started out as a noun, it was also considered correct to add -ly and make it an adverb. Only recently has it been adopted as a verb.
Now whether this is erosion or just the natural evolution of the spoken word, is a judgement call. How we speak and write to day is very different from Dickens time, and many of the great literary works of the past, would get rejected by most publishers today.