Which of the following compounds has a lattice enthalpy lower than its hydration enthalpy?

Which of the following orders is correct $:-$

Mortar is a mixture of which of the following?

The pair of amphoteric hydroxides is

What is the chemical formula of Plaster of Paris?

Given below are two statements,one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A:$ Beryllium has a less negative value of reduction potential compared to the other alkaline earth metals.
Reason $R:$ Beryllium has large hydration energy due to the small size of $Be^{2+}$ but a relatively large value of atomization enthalpy.
In the light of the above statements,choose the most appropriate answer from the options given below.