Which of the following set of metals have strong tendency to form super oxides?

Identify the correct statements with respect to compounds of beryllium.

I. Beryllium oxide is amphoteric in nature.

II. Beryllium hydride is formed by the reaction of beryllium with hydrogen.

III. Beryllium hydride is formed by the reaction of beryllium chloride with lithium aluminium hydride.

IV. Beryllium sulpahte is the least soluble sulphate among the sulphates of alkaline earth metals.

Unknown inorganic compound ' $A$ ' is used for water softening. ' $A$ ' reacts with $\mathrm{Na}_2 \mathrm{CO}_3$ to generate an alkaline compound ' $B$ ' whose $\mathrm{pH}=14$. ' $A$ ' on reaction with $\mathrm{CO}_2$ gives cloudy ppt. ' $B$ ' +CaO reacts with unknown organic compound ' $C$ ' to give $\mathrm{C}_6 \mathrm{H}_6$. $A$, $B$ and $C$, respectively, are

The correct order of melting points of the following salts is

$$ \begin{array}{lll} \text { LiCl } & \text { LiF } & \text { Lil } \\ \text { I } & \text { II } & \text { III } \end{array} $$