Identify the metal halide from the following that has the highest ionic character? ($M =$ metal atom)

Which of the following has the lowest melting point?

Highest covalent character is found in which of the following?

The order of covalent character of $KF, KCl, KI$ is

Which compound has the lowest melting point?

How would you explain the following observations?
$(i)$ $BeO$ is almost insoluble but $BeSO_4$ is soluble in water.
$(ii)$ $BaO$ is soluble but $BaSO_4$ is insoluble in water.
$(iii)$ $LiI$ is more soluble than $KI$ in ethanol.