Which one of the following will react most vigorously with water?

Identify the incorrect reaction from the following.

Which of the following is basic in nature?

Why are alkali metals not found in nature?

Which of the following is not a product,when $RbO_2$ reacts with $H_2O$?

The correct statements are:
$I$. The low solubility of $LiF$ is due to its high lattice enthalpy.
$II$. $LiBr$ is soluble in acetone.
$III$. $LiCl$ is soluble in pyridine.
$IV$. The order of melting points of alkali metal halides is $MF > MCl > MBr > MI$.