In the presence of which of the following does magnesium continue to burn?

Sodium oxide $(Na_2O)$ is produced when

$Mg$ is obtained by:

What is produced when $Mg$ burns in $CO_2$?

Which of the following statements is $CORRECT$?

Consider the following statements.
$I$. $Cs^{+}$ ion is more highly hydrated than other alkali metal ions.
$II$. Among the alkali metals,only lithium forms a stable nitride by direct combination with nitrogen.
$III$. Among the alkali metals $Li, Na, K, Rb$,the metal $Rb$ has the highest melting point.
$IV$. Among the alkali metals $Li, Na, K, Rb$,only $Li$ forms peroxide when heated with oxygen.
Select the correct statement.