  In loop quantum cosmology, the slow-roll inflation is generic, and when the
kinetic energy of the scalar field dominates at the bounce, the evolution of
the Friedmann-Lema\^itre-Robertson-Walker universe will go through three
distinguishable epochs, bouncing, transition, and finally slow-roll inflation,
before the reheating commences. The bouncing dynamics are insensitive of the
potential and initial conditions, so that the expansion factor and the scalar
field can be described uniquely by a universal solution during this epoch.
After about $10^5$ Planck time, the epoch of transition starts and the universe
rapidly turns over from the kinetic energy dominated state to the potential
energy dominated one, whereby the slow-roll inflationary phase begins. In this
paper, we consider the power law plateau potential and study the
pre-inflationary cosmology for different sets of initial conditions, so that
during the slow-roll inflation epoch enough e-folds will be produced.
Considering the generalized reheating and comparing with the recent Planck 2018
data, we are able to constrain the total number of e-folds ($N_T$) from the
bounce till today to be consistent with the current observable universe.
Depending on the matter driving the reheating (subject to the different
dominant equations of states), we report the observationally allowed $N_T$ and
reheating temperature and find in particular $N_T \simeq 127$, which is
significantly different from the one $N_T \gtrsim 141$ obtained previously
without considering the reheating phase.
