Which of the following statements is not correct?

Dihydrogen can be prepared by which of the following reactions?
$(I)$ Reaction of granulated $Zn$ with dil. $HCl$
$(II)$ Reaction of $Zn$ with aq. $NaOH$
$(III)$ By heating calcium hydrogen carbonate

The correct statements among $(a)$ to $(d)$ regarding $H_2$ as a fuel are:
$(a)$ It produces fewer pollutants than petrol.
$(b)$ $A$ cylinder of compressed dihydrogen weighs $\sim 30$ times more than a petrol tank producing the same amount of energy.
$(c)$ Dihydrogen is stored in tanks of metal alloys like $NaNi_5$.
$(d)$ On combustion,the values of energy released per gram of liquid dihydrogen and $LPG$ are $142$ and $50 \ kJ,$ respectively.

Which physical property of dihydrogen $(H_2)$ is wrong?

In which of the following reactions,hydrogen is acting as an oxidising agent?

Write a note on covalent or molecular hydrides.