Which of the following reactions yields biphenyl from chlorobenzene?

In the following reaction,the structure of the major product '$X$' is

What is the product $X$ in the following Wurtz-Fittig reaction?

The set of compounds in which the reactivity of the halogen atom in ascending order is:

Aryl halides are extremely less reactive towards nucleophilic substitution. Predict and explain the order of reactivity of the following compounds towards nucleophilic substitution:
$(I)$ $p$-nitrochlorobenzene
$(II)$ $2,4$-dinitrochlorobenzene
$(III)$ $2,4,6$-trinitrochlorobenzene

Which sequence represents the best synthesis of $4-$isopropylbenzonitrile?