Which of the following is not used as an explosive?

Assertion : $S_{N}2$ reactions always proceed with inversion of configuration.
Reason : $S_{N}2$ reaction of an optically active aryl halide with an aqueous solution of $KOH$ always gives an alcohol with opposite sign of rotation.

The major product of the reaction is:

The main product of the following reaction will be:

Why do aryl halides undergo electrophilic substitution reactions at $o-$ and $p-$positions? Why are they less reactive than benzene?

The main product of the following reaction will be
$1$-fluoro-$2$-chloro-$4$-nitrobenzene + piperidine $\to$ Product