Which of the following properties is $NOT$ correct for alkali metals?

Identify the correct statements from the following :
$I$. Tendency to form halide hydrates gradually increases from $Be$ to $Ba$ down the group.
$II$. Tendency to form stable superoxides increases from $Li$ to $Cs$ down the group.
$III$. Low solubility of $LiF$ is due to its high lattice energy.
$IV$. Solubility of carbonates of group-$2$ elements increases down the group.

Match Column $-I$ with Column $-II$ :

Column $-I$	Column $-II$
$(a)$. Super oxide	$(p)$. $Na_2O_2$
$(b)$. Peroxide	$(q)$. $CO_2$
$(c)$. Dioxide	$(r)$. $C_3O_2$
$(d)$. Sub oxide	$(s)$. $CsO_2$

To which group do the following elements belong? Which of them has the highest metallic character?
$K, Na, Li, Rb$

Which of the following has maximum solubility in water?

What is obtained by the decomposition of sodium nitrate at temperatures above $800\,^oC$?