Which amino acid is present as a monomer in the polymer $Nylon-2-nylon-6$?

Type of amino acids obtained by hydrolysis of proteins is :

The total number of amino acids present in insulin is

Amino acids containing a heterocyclic ring are:
$(i)$ Histidine
$(ii)$ Valine
$(iii)$ Arginine
$(iv)$ Proline

Which of the following statements is correct?

$1.78 \ g$ of an optically active $L$-amino acid $(A)$ is treated with $NaNO_{2} / HCl$ at $0^{\circ}C$. $448 \ cm^{3}$ of nitrogen at $STP$ is evolved. $A$ sample of protein has $0.25 \%$ of this amino acid by mass. The molar mass of the protein is