What is the end of a polypeptide chain that contains a free amino group called?

If one end of a polypeptide chain contains an $NH_2$ group,what does the other end contain?

Assertion : The amino acid glycine comes under the category of nonessential amino acids.
Reason : This is due to the fact that it can not be synthesised in the body.

Select the correct match for $X$ and $Y$:

Column $X$	Column $Y$
$(1)$ Primary protein	$(P)$ Globular or fibrous form
$(2)$ Secondary protein	$(Q)$ Three-dimensional arrangement of a single polypeptide chain
$(3)$ Tertiary protein	$(R)$ Gene-controlled
$(4)$ Quaternary protein	$(S)$ Helical or pleated sheet form

Which of the following statement$(s)$ is/are true?
$(i)$ All amino acids contain one chiral centre.
$(ii)$ Some amino acids contain one, while some contain more chiral centres or even no chiral centre.
$(iii)$ All amino acids in proteins have $L$-configuration.
$(iv)$ All amino acids found in proteins have $1^{\circ}$ amino group.

Which is the most abundant protein in the animal kingdom?