Which of the following orders are correct?
$(I)$ Thermal stability: $BeSO_4 < MgSO_4 < CaSO_4 < SrSO_4$
$(II)$ Basic nature: $ZnO > BeO > MgO > CaO$
$(III)$ Solubility in water: $LiOH > NaOH > KOH > RbOH$
$(IV)$ Melting point: $NaCl > KCl > RbCl > CsCl > LiCl$

Present a comparative account of the alkali and alkaline earth metals with respect to the following characteristics :
$(a)$ Tendency to form ionic/covalent compounds.
$(b)$ Nature of oxides and their solubility in water.
$(c)$ Formation of oxosalts.
$(d)$ Solubility of oxosalts.
$(e)$ Thermal stability of oxosalts.

$A$ white solid '$A$' on heating produces a gas that turns lime water milky,and the remaining solid residue is yellow when hot but turns white on cooling. The solid '$A$' is:

Select the incorrect order.

Compare the alkali metals and alkaline earth metals with respect to $(i)$ ionization enthalpy,$(ii)$ basicity of oxides,and $(iii)$ solubility of hydroxides.

Assertion : $Al(OH)_3$ is insoluble in $NH_4OH$ but soluble in $NaOH$.
Reason : $NaOH$ is a strong alkali.