  This article represents quantitative numerical analysis to find the
sensitivity for the mass ordering and octant of atmospheric mixing angle
$\theta_{23}$ within 3$\sigma$ range of oscillation parameters, in the context
of three long base line (LBL) accelerator experiments viz. UNO, DUNE and
NO$\nu$A.
  We notice that on the basis of quantitative sensitivity pertaining to the
event rate, it is possible to investigate the mass ordering within all
experiments. Conclusively, like NO$\nu$A and DUNE experiments, UNO experiment
stands as better alternative for investigating mass ordering, especially when
we need to cross check the results at higher beam energies and base line
lengths.
  We observe that discrete solutions viz. {\it wrong octant-right
$\delta_{CP}$, wrong octant-wrong $\delta_{CP}$} and {\it right octant-wrong
$\delta_{CP}$} and continuous solutions arising due to submergence of discrete
solutions with true solution are possible up to 3$\sigma$ level. It is UNO
experiment that alone have the potential to remove these discrete solutions,
while both NO$\nu$A and DUNE experiments have very poor tendency to remove
these discrete solutions especially near the maximal mixing. We find that these
discrete solutions can be resolved up to 3$\sigma$ level by the combined
NO$\nu$A+DUNE+UNO data set, at all multiple degenerate solutions in the true
parameter space considered under the study. Though replacing half the neutrino
run with antineutrino run introduces qualitative advantage because of their
different dependences on $\delta_{CP}$, but due to lower cross section and
reduction in the statistics, addition of antineutrino data make the precision
worse. Thus considering experimental data only in the neutrino mode, enhances
$\delta_{CP}$ and $\theta_{23}$ precision significantly.
