Peptide is another name for protein, but is usually used for shorter amino acid chains.
No, a peptide bond is made between two amino acids to make polypeptides or proteins. Carbohydrates (sugars) do not make peptide bonds.
A pentapeptide, for example, is five amino acids conjoined by standard peptide bonds.
Methadone is a synthetic opiod.
Yes, OxyContin is a synthetic opioid.