Limestone is heated strongly to give a gas X and a solid Y. Y is heated with coke at about 2300 K in an electric furnace to give a solid Z (and carbon monoxide). Z reacts with water to give a gas W and a base. Which statements are correct?

1. AZ is calcium carbide, $\mathrm{CaC}{}_2$.
2. BY dissolves in aqueous $\mathrm{NaOH}$ because it is amphoteric.
3. CX turns lime water milky.
4. DW is ethyne, which burns with a sooty flame.