  Supersymmetric (SUSY) grand unified theories (GUTs) appear to be best
motivated for understanding strong, weak and electromagnetic interactions of
nature. We briefly review emergence of new formulas for running fermion masses
valid in direct breaking of GUTs. High scale mixing unification of quark and
neutrino mixings and existence of theorems on vanishing theoretical
uncertainties in GUT predictions are discussed. D-Parity properties of SO(10)
representations leading to large number of intermediate breaking models are
pointed out. Unification predictions of SUSY SO(10) in the light of neutrino
mass, lepton flavor violation, baryogenesis via leptogenesis within gravitino
constraint, and proton decay are noted. We further discuss realisation of
flavour unification and possibility of fitting all fermion masses through
R-Parity and D-Parity conserving left-right symmetric intermediate breaking in
SUSY SO(10)$\times S_4$. In the absence of SUSY two interesting possibilities
of minimal grand desert modifications with only one intermediate mass scalar in
each case and their applications to dark matter decay through type-I seesaw are
briefly noted. Heavy scalar triplet decay leptogenesis through new ansatz for
type-II seesaw dominance in non-SUSY SO(10), emergence of new CP asymmetry
formulas and model capabilities to explain WIMP dark matter, vacuum stability
of the scalar potential and experimentally observed limit on proton lifetime
are briefly summarized.
