Which compound on heating produces a coloured metal oxide finally?

The two major constituents of Portland cement are

To distinguish between $A$ and $B$,it is observed that both elements form oxides,but $B$ also forms a nitride when burnt in air. What are $A$ and $B$?

The pair$(s)$ of reagents that yield paramagnetic species is/are:
$A$. $Na$ and excess of $NH_3$
$B$. $K$ and excess of $O_2$
$C$. $Cu$ and dilute $HNO_3$
$D$. $O_2$ and $2-ethylanthraquinol$

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: $NaCl > KCl > RbCl > CsCl > LiCl$

Match the following:

Metal	Uses
$1$. Sodium	$a$. For preparing springs
$2$. Beryllium-copper	$b$. In treatment of cancer
$3$. Radium	$c$. In preparation of aeroplanes
$4$. Magnesium-aluminium	$d$. In color industries