Among the nitrates of alkali metals,which one can be decomposed to its oxide on strong heating?

Which of the following statements is incorrect?

What is obtained when sodium metal is heated in a stream of dry ammonia?

Which one of the following alkali metals gives hydrated salts?

Among the following,the number of metals that can be used as electrodes in a photoelectric cell is $.......$ (Integer answer)
$A. Li$
$B. Na$
$C. Rb$
$D. Cs$

The correct order of electrical conductivity of alkali metal ions in their aqueous solution for $Cs^{+}$, $K^{+}$, $Na^{+}$, and $Li^{+}$ is: