The correct order of increasing solubility in water is

Which alkali metal during flame test will show color corresponding to maximum wavelength?

Which of the alkali metals has the lowest melting point?

Which of the following statements about $Na_2O_2$ is not correct?

The chemical formulas of $A$,$B$,and $C$ are:
$A + Na_2CO_3 \to B + C$
$A \xrightarrow{CO_2} \text{Milky cloud}, C$

Identify the correct statements from the following:
$A$) Among alkali metal ions,$Li^+$ has the highest hydration enthalpy.
$B$) The boiling point of alkali metals increases from $Li$ to $Cs$.
$C$) The density of $K$ is less than that of $Na$ and $Rb$.
$D$) $Li$ has a strong tendency to form superoxide.