  The Supersymmetric SO(10) GUT based on the ${\bf{210\oplus 10\oplus 120\oplus
126\oplus {\bar{126}}}}$ Higgs system has 40 real superpotential parameters of
which 2 can be fixed by the Light Higgs doublet fine tuning and one by the
determination of the unification scale by the RG flow. It provides a minimal
framework for the emergence of R-parity exact Supersymmetric Standard Model at
low energies and viable supersymmetric seesaw explanation for the observed
neutrino masses and mixing angles. We present complete formulae for MSSM
decomposition of the superpotential invariants, explicit GUT scale one step
spontaneous symmetry breaking down to the MSSM, tree level light charged
fermion effective yukawa couplings, Weinberg neutrino mass generation operator,
and the complete set of effectve superpotential coefficients of LLLL and RRRR
$d=5$ Baryon violating operators(which have contributions from novel
\textbf{120}-plet Higgs channels) in terms of GUT superpotential parameters. We
survey the gauge RG flow including threshold corrections due to the calculated
super heavy particle spectra. The formulae given are used in following papers
to determine complete realistic Susy SO(10) GUT fits of all MSSM data.
