Which of the following is an example of a protein?

Which amino acid contains a secondary amino group in its structure?

Assertion $(A)$: In aqueous solution,amino acids exist in dipolar ion form.
Reason $(R)$: Most of the naturally occurring amino acids have $L$-configuration.
The correct option among the following is:

Match the $LIST$-$I$ with $LIST$-$II$:

List-$I$ (Amino acid)	List-$II$ (Positive reaction/Test for functional group present in side chain of amino acid)
$A$. Glutamine	$I$. Hinsberg's test
$B$. Lysine	$II$. Neutral $FeCl_3$ test
$C$. Tyrosine	$III$. Ceric ammonium nitrate test
$D$. Serine	$IV$. Hoffman bromamide degradation

Observe the structures of the following compounds:
$1$. $2$-chlorobutane
$2$. Glycine $(NH_2CH_2COOH)$
$3$. Alanine $(CH_3CH(NH_2)COOH)$
$4$. Styrene $(C_6H_5CH=CH_2)$
$5$. Menthol
The total number of structures/compounds which possess asymmetric carbon atoms is $....$

Explain the classification of proteins based on their molecular structure.