  We report comprehensive spectral and temporal properties of the Be/X-ray
binary pulsar SMC X-2 using X-ray observations during the 2015 and 2022
outbursts. The pulse profile of the pulsar is unique and strongly luminosity
dependent. It evolves from a broad-humped into a double-peaked profile above
luminosity 3$\times$10$^{38}$ ergs s$^{-1}$. The pulse fraction of the pulsar
is found to be a linear function of luminosity as well as energy. We also
studied the spectral evolution of the source during the latest 2022 outburst
with NICER. The observed photon index shows a negative and positive correlation
below and above the critical luminosity, respectively, suggesting evidence of
spectral transition from the sub-critical to super-critical regime. The
broadband spectroscopy of four sets of NuSTAR and XRT/NICER data from both
outbursts can be described using a cutoff power-law model with a blackbody
component. In addition to the 6.4 keV iron fluorescence line, an
absorption-like feature is clearly detected in the spectra. The cyclotron line
energy observed during the 2015 outburst is below 29.5 keV, however latest
estimates in the 2022 outburst suggest a value of 31.5 keV. Moreover, an
increase of 3.4 keV is detected in the cyclotron line energy at equal levels of
luminosity observed in 2022 with respect to 2015. The observed cyclotron line
energy variation is explored in terms of accretion induced screening mechanism
or geometrical variation in line forming region.
