Which of the following is true for diamond?

Which of the following statements are correct?
$(a)$ The isotope of carbon containing $7$ neutrons has natural abundance of $1.1 \%$.
$(b)$ Among the $IV$ $A$ group elements, $Sn$ has the lowest melting point.
$(c)$ Silicon is the $2^{nd}$ (by mass) most abundant element in the earth's crust.
$(d)$ Elemental carbon shows the highest electrical resistivity among the $14$ group elements.

$NaHSO_3$ is heated to produce $H_2O$ and compound $'A'$. Which of the following statements is $INCORRECT$ about $'A'$?

Explain the physical properties of group $14$ elements.

Which of the following is an example of a neutral oxide?

Diamond and emerald are forms of which of the following respectively?