  In this research, we explore the semiclassical approximation to canonical
quantum gravity and how a classical background emerges from the Wheeler-DeWitt
(WDW) states. By employing the Wigner functional analysis, we derive the
backreacted Einstein-Hamilton-Jacobi equation as an approximation to the WDW
equation, along with the requisite validity conditions. We then apply this
understanding to both AdS/CFT and dS/CFT correspondences in conjunction with
Cauchy slice holography, to explain how the bulk is encoded in the correlation
functions of the dual field theory.
  We then explain an appropriate description for scenarios in which gravity
behaves quantum mechanically in certain regions of spacetime and explain its
relation to subregion holography. We derive the validity conditions for gravity
to be semiclassical near any co-dimension 1 time-like surface and employ these
conditions to explore the black hole information paradox. Our analysis suggests
that for evaporating black holes, there might be a violation of semiclassical
gravity in the near-horizon region close to the Page time, although this is
contingent upon certain assumptions. This also provides insights into the fate
of information trapped within evaporating black holes. We then explore this
issue from the perspectives of both external and infalling observers. We then
explain how to employ the framework of Cauchy slice holography to study the
retrieval of information from evaporating black holes, presenting a
comprehensive approach to tackle this complex issue in quantum gravity.
