  The Two-Higgs-Doublet-Standard Model-Axion-Seesaw-Higgs-Portal inflation
(2hdSMASH) model consisting of two Higgs doublets, a Standard Model (SM)
singlet complex scalar and three SM singlet right-handed neutrinos can embed
axion dark matter, neutrino masses and address inflation. We report on an
investigation of the inflationary aspects of 2hdSMASH and its subsequent impact
on low energy phenomenology. In particular, we identify inflationary directions
for which the parameter values required for successful inflation do not violate
perturbative unitarity and boundedness-from-below conditions. By analyzing the
renormalization-group flow of the parameters we identify the necessary and
sufficient constraints for running all parameters perturbatively and
maintaining stability from the electroweak to the PLANCK scale. We observe that
stringent constraints arise on the singlet scalar self coupling from
inflationary constraints, i.e, $\lambda_S\sim 10^{-10}$. Further, we find that
all theoretical and experimental constraints are satisfied if the portal
couplings are typically in the range $(\frac{v}{v_S})$ and $(\frac{v}{v_S})^2$
(where $v, v_S$ refer to the electroweak and singlet scalar vacuum expectation
value respectively). As a consequence, inflation is realized in a variety of
field space directions in the effective single field regime. Finally we provide
testable benchmark scenarios at colliders.
