Which of the following elements is chemically most reactive?

Name an element from Group $2$ which forms an amphoteric oxide and a water soluble sulphate.

Which of the following ions has the largest heat of hydration?

Select the incorrect order of solubility.

Alkaline earth metals belong to the

Identify the correct statements from the following:
$I$. All alkaline earth metals give hydrides on heating with hydrogen.
$II$. Calcium hydroxide is used to purify sugar.
$III$. $BeCl_2$ is a dimer in gaseous phase.