Magnesium does not decompose which of the following?

In context with beryllium,which one of the following statements is incorrect?

The most electropositive amongst the alkaline earth metals is

Which of the following hydrides are ionic?

$BeO$ reacts with $HF$ in the presence of ammonia to give $[A]$,which on thermal decomposition produces $[B]$ and ammonium fluoride. The oxidation state of $Be$ in $[A]$ is $.....$.

Match List-$I$ with List-$II$ for the compositions of substances and select the correct answer using the code given below the lists.

List-$I$ Substances	List-$II$ Composition
$A$. Plaster of paris	$i$. $CaSO_4.2H_2O$
$B$. Epsomite	$ii$. $CaSO_4.\frac{1}{2}H_2O$
$C$. Kieserite	$iii$. $MgSO_4.7H_2O$
$D$. Gypsum	$iv$. $MgSO_4.H_2O$
	$v$. $CaSO_4$