Hydrogen forms a stable diatomic molecule like which elements?

Which of the following statements are correct?
$(i)$ $NaH_{(s)}$ reacts violently with water to form $NaOH$ and $H_2$
$(ii)$ An example for electron rich hydride is $NH_3$
$(iii)$ Nickel forms saline hydride

On heating,hydrazoic acid forms:

Given below are two statements :
Statement-$I$: The process of producing syn-gas is called gasification of coal.
Statement-$II$: The composition of syn-gas is $CO + H_2$ ($1 : 1$ ratio).
In the light of the above statements,choose the most appropriate answer from the options given below:

The charring of sugar takes place when treated with concentrated $H_2SO_4$. What is the type of reaction involved in it?

How do you expect the metallic hydrides to be useful for hydrogen storage? Explain.