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

Thermal stability of $MCO_3$ is in order:

Addition of an oxalate solution to an aqueous solution containing a mixture of $Ba^{2+}$,$Sr^{2+}$,and $Ca^{2+}$ ions will precipitate:

An element reacts with hydrogen to form a compound $A$,which on treatment with water liberates hydrogen gas. The element can be

The metal $X$ is prepared by the electrolysis of fused chloride. It reacts with hydrogen to form a colourless solid from which hydrogen gas is released on treatment with water. The metal is

Which of the following salts can accommodate the largest number of $H_2O$ molecules per molecule in their halide hydrates?