Which of the following is not a classification of proteins?

Type of amino acids obtained by hydrolysis of proteins is :

The structure of $Gly-Ala$ is

Which of the following amino acids is optically inactive?

Assertion $(A)$: In aqueous solution,$\alpha$-amino acids exist as an internal salt called a zwitter ion.
Reason $(R)$: Proline is a natural amino acid having a secondary amino group. The correct option among the following is:

The helical structure of proteins is stabilized by