Verified answer

An amino acid is a single molecule, so you cannot sequence it. You can analyze a protein to see the relative amounts of what amino acids are in it using chromatography, but this will not tell you the order they were in.

I think maybe you are talking about sequencing a peptide. This is something you would want to do if you isolate a certain protein and are interested in what it does. You would want to learn about its structure to later figure out which pieces are important for what functions.

Nowadays, there are automated sequencers that can do this for us by doing an edman degredation reaction multiple times (this reaction identifies the N terminal amino acid).

You usually need to denature the protein to its primary structure before sequencing.