Hydrogen gas is evolved by the action of cold dilute $HNO_3$ on which of the following metals?

How many of the following metals give oxides and nitrides when burnt in air?
$Be, Na, Mg, Ba, Sr, Li, K$

Assertion $(A): K, Rb$ and $Cs$ form superoxides. \\ Reason $(R):$ The stability of superoxides increases from $K$ to $Cs$ due to decrease in lattice energy.

Which of the following is thermally decomposable?

Hydrated sodium aluminium silicate is called

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.