Which of the following statements is $NOT$ correct?

Alkali metals react with water to form hydroxides and release hydrogen gas. This is because:

Two metals $A$ and $B$ having similar ionic radii,react with oxygen to give only monoxides and react with nitrogen to give nitrides. Then,$A$ and $B$ respectively are

The alkali metals which form normal oxide,peroxide,as well as superoxides are:

For the alkali metals,which of the following increases with increasing atomic number?

Comment on each of the following observations:
$(a)$ The mobilities of the alkali metal ions in aqueous solution are
$Li^{+} < Na^{+} < K^{+} < Rb^{+} < Cs^{+}$
$(b)$ Lithium is the only alkali metal to form a nitride directly.
$(c)$ $E^{\circ}$ for $M^{2+}_{(aq)} + 2e^{-} \longrightarrow M_{(s)}$ (where $M = Ca, Sr$ or $Ba$) is nearly constant.