What is insulin?

$A$ quaternary protein consisting of two $\alpha$-chains and two $\beta$-chains is:

In the secondary structure of a polypeptide chain,the folding of the chain is due to which type of bond?

Which statement is correct for biomolecules?

Statement $- I :$ All amino acids are protein-forming amino acids.
Statement $- II : R-$ group is a variable group in an amino acid.

What is the macromolecular polymer formed by amino acids called?