How does Plaster of Paris become hard?

What are the products formed when an aqueous solution of magnesium bicarbonate is boiled?

What is obtained when gypsum is heated at $300\,^oC$?

Which of the following alkaline earth metals does not exhibit colour when heated in a flame?

Given below are two statements:
Statement $I$: None of the alkaline earth metal hydroxides dissolve in alkali.
Statement $II$: Solubility of alkaline earth metal hydroxides in water increases down the group.
In the light of the above statements,choose the most appropriate answer from the options given below:

Which of the following salts is not soluble in water?