What is obtained by the reaction of $HCOOH$ with concentrated $H_2SO_4$?

Match the following types of hydrides in List-$I$ with their examples in List-$II$.

List-$I$ (Type of hydride)	List-$II$ (Example)
$(A)$ Electron precise	$(i)$ $SiH_4$
$(B)$ Saline	$(ii)$ $H_2O$
$(C)$ Electron deficient	$(iii)$ $MgH_2$
$(D)$ Electron rich	$(iv)$ $B_2H_6$

Identify the correct statements from the following:
$i$. Reaction of hydrogen with fluorine occurs even in dark.
$ii$. Manufacture of ammonia by Haber process is an endothermic reaction.
$iii$. $HF$ is an electron-rich hydride.

Which one of the following substances is used in the laboratory for a fast drying of neutral gases?

Which of the following is true for the industrial production of hydrogen from water gas $(CO + H_2)$?

What do you understand by $(i)$ electron deficient,$(ii)$ electron precise,and $(iii)$ electron rich compounds of hydrogen? Provide justification with suitable examples.