  Giving up the solutions to the fine-tuning problems, we propose the
non-supersymmetric flipped $SU(5)\times U(1)_X$ model based on the minimal
particle content principle, which can be constructed from the four-dimensional
$SO(10)$ models, five-dimensional orbifold $SO(10)$ models, and local F-theory
$SO(10)$ models. To achieve gauge coupling unification, we introduce one pair
of vector-like fermions, which form complete $SU(5)\times U(1)_X$
representation. Proton lifetime is around $5\times 10^{35}$ years, neutrino
masses and mixing can be explained via seesaw mechanism, baryon asymmetry can
be generated via leptogenesis, and vacuum stability problem can be solved as
well. In particular, we propose that inflaton and dark matter particle can be
unified to a real scalar field with $Z_2$ symmetry, which is not an axion and
does not have the non-minimal coupling to gravity. Such kind of scenarios can
be applied to the generic scalar dark matter models. Also, we find that the
vector-like particle corrections to the $B_s^0$ masses can be about 6.6%, while
their corrections to the $K^0$ and $B_d^0$ masses are negligible.
