  In this paper, we initially derive the equivalent fractional integral
equation to $\Psi$-Hilfer hybrid fractional differential equations and through
it, we prove the existence of a solution in the weighted space. The primary
objective of the paper is to obtain estimates on $\Psi$-Hilfer derivative and
utilize it to derive the hybrid fractional differential inequalities involving
$\Psi$-Hilfer derivative. With the assistance of these fractional differential
inequalities, we determine the existence of extremal solutions, comparison
theorems and uniqueness of the solution.
