Thermal decomposition of which of the salt listed below yields a basic and an acidic oxide simultaneously?

Which of the following substances is unlikely to contain $CaCO_3$?

The compound $A$ on heating gives a colourless gas and a residue that is dissolved in water to obtain $B$. Excess of $CO_2$ is bubbled through aqueous solution of $B$,$C$ is formed which is recovered in the solid form. Solid $C$ on gentle heating gives back $A$. The compound $A$ is:

Given below are two statements:
Statement $I$: Both $CaCl_2 \cdot 6H_2O$ and $MgCl_2 \cdot 8H_2O$ undergo dehydration on heating.
Statement $II$: $BeO$ is amphoteric whereas the oxides of other elements in the same group are acidic.
In the light of the above statements,choose the correct answer from the options given below:

Which of the following reactions does not take place?

Which of the following sulfates is insoluble in water?