Under which conditions do proteins get denatured?

How many types of amino acids are found in the structure of proteins?

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.

The most abundant protein in the whole biosphere is:

Nitrogen is an important constituent of

Which of the following amino acids contains a non-polar '$R$' group?