Most of the metal oxides are insoluble in water but some dissolve in water. What are these oxides and their solution in water called ?

Q. A metal $M$ readily forms water-soluble sulphate $MS{O}_4$, water-insoluble hydroxide $M(OH{)}_2$ and oxide $MO$. The oxide and hydroxide are soluble in $NaOH$. The $M$ is:

Q. A metal M readily forms water soluble $MS{O}_4$. It also forms oxide MO which becomes inert on heating. Hydroxide $M(OH{)}_2$ is insoluble in water but soluble in NaOH solution. What is M?

Q. Assertion :Coal contains some compounds of sulphur and nitrogen. Reason: During rain, these oxides dissolve in rain water and are known to cause acid rain.

Q. Metallic oxides are basic, and non-metallic oxides are acidic in nature. Which of the following oxides will change the colour of blue litmus to red when dissolved in water?​