  We present a comprehensive study of GRS 1915+105 in wide energy band
($0.5-60$ keV) using AstroSat observations during the period of $2016-2019$.
The MAXI X-ray lightcurve of the source shows rise and decay profiles similar
to canonical outbursting black holes. However, the source does not follow the
exemplary 'q'-diagram in the Hardness-Intensity Diagram (HID). Model
independent analysis of lightcurves suggests that GRS 1915+105 displays various
types of variability classes ($\delta,\chi,\rho,\kappa,\omega$ and $\gamma$).
We also report possible transitions from one class to another
($\chi\rightarrow\rho,\rho\rightarrow\kappa$ via an 'unknown' class and
$\omega\rightarrow\gamma\rightarrow\omega+\gamma$) within a few hours duration.
Broadband energy spectra are well modeled with multi-coloured disc blackbody
and Comptonised components. We explore the 'spectro-temporal' features of the
source in the different variability classes, transitions between classes, and
evolution during $2016-2019$. Detailed analysis indicates a gradual increase in
the photon index ($\Gamma$) from $1.83$ to $3.8$, disc temperature ($kT_{in}$)
from $1.33$ to $2.67$ keV, and Quasi-periodic Oscillation (QPO) frequency
($\nu$) from $4$ to $5.64$ Hz during the rise, while the parameters decrease to
$\Gamma$ ~$1.18$, $kT_{in}$ ~$1.18$ keV, and $\nu$ ~$1.38$ Hz respectively in
the decline phase. The source shows maximum bolometric luminosity (L$_{bol}$)
during the peak at ~$36$% of Eddington luminosity (L$_{EDD}$), and a minimum of
~$2.4$% L$_{EDD}$ during the decay phase. Further evolution of the source
towards an obscured low-luminosity (L$_{bol}$ of ~ 1% L$_{EDD}$) phase, with a
decrease in the intrinsic bolometric luminosity of the source due to
obscuration, has also been indicated from our analysis. The implication of our
results are discussed in the context of accretion disc dynamics around the
black hole.
