Which of the following salts does not give a flame test?

Which of the following statements is incorrect?

$X + C + Cl_2 \xrightarrow[> 1000 \ K]{\text{High temp.}} Y + CO$
$Y + 2H_2O \to Z + 2HCl$
Compound $Y$ is found in a polymeric chain structure and is an electron-deficient molecule. $Y$ must be:

The composition formula of gypsum is

Explain the chemical properties of alkaline earth metals (Group $2$) in detail.

Chemical $A$ is used for water softening to remove temporary hardness. $A$ reacts with $Na_2CO_3$ to generate caustic soda. When $CO_2$ is bubbled through $A$,it turns cloudy. What is the chemical formula of $A$?