Which gas is evolved when potassium ferrocyanide crystals are heated with concentrated $H_2SO_4$?

Which of the following statements are correct?
$(i)$ $CCl_4$ undergoes hydrolysis easily
$(ii)$ Diamond has directional covalent bonds
$(iii)$ Fullerene is the thermodynamically most stable allotrope of carbon
$(iv)$ Glass is a man-made silicate
The correct answer is

In the carbon family,elements other than carbon do not form $p\pi - p\pi$ bonds because their atomic radii are very ........

The $[SiO_4]^{4-}$ unit has a tetrahedral structure. Which silicate is formed by sharing three oxygen atoms per $[SiO_4]^{4-}$ unit?

Give reasons:
$(i)$ Conc. $HNO_3$ can be transported in aluminium container.
$(ii)$ $A$ mixture of dilute $NaOH$ and aluminium pieces is used to open drain.
$(iii)$ Graphite is used as lubricant.
$(iv)$ Diamond is used as an abrasive.
$(v)$ Aluminium alloys are used to make aircraft body.
$(vi)$ Aluminium utensils should not be kept in water overnight.
$(vii)$ Aluminium wire is used to make transmission cables.

Sulphur is most soluble in