  Recently there is progress to resolve the issue regarding the non-existence
of the Cauchy horizon inside the static, charged, and spherically symmetric
black holes. However, when we generically extend the black holes' spacetime,
they are not just static but can be dynamical, thus the interior of black holes
does not remain the same as the static case when we take into account the
dynamical evolution of black holes. Then, our aim in this paper is to provide a
few constructive insights and guidelines regarding this issue by revisiting a
few examples of the gravitational collapse of spherically symmetric charged
black holes using the double-null formalism. Our numerical results demonstrate
that the inside of the outer horizon is no longer static even in late time, and
the inner apparent horizon exists but is not regular. The inner apparent
horizon can be distinguished clearly from the Cauchy horizon. The spherical
symmetric property of black holes allows the inner horizon to be defined in two
directions, i.e., the differentiation of the areal radius vanishes along either
the out-going or the in-going null direction. Moreover, the Cauchy horizon can
be generated from a singularity. Still, the notion of the singularity can be
subtle where it can have a vanishing or non-vanishing areal radius; the
corresponding curvature quantities could be finite or diverge, although the
curvatures can be greater than the Planck scale. Finally, we show some examples
that the "hair" which is associated with the matter field on the inner horizon
is not important to determine the existence of the Cauchy horizon; rather, the
hair on the outer horizon might play an important role on the Cauchy horizon.
Therefore, the dynamic properties of the interior of charged black holes could
shed light for us to understand deeply about the Cauchy horizon for the
extensions of no-Cauchy-horizon theorems.
