We discuss the Higgs boson mass sum rules in the Minimal Supersymmetric
Standard Model in order to estimate the upper limits on the masses of stop
quarks as well as the lower bounds on the masses of the scalar Higgs boson
state. The bounds on the scale of quark-lepton compositeness derived from the
CDF Collaboration (Fermilab Tevatron) data and applied to new extra gauge boson
search is taken into account. These extra gauge bosons are considered in the
framework of the extended SU(2)_h \times SU(2)_l model. In addition, we discuss
the physics of rare decays of the MSSM Higgs bosons in both CP-even and CP-odd
sectors and also some extra gauge bosons.Comment: 24 pages, LaTeX, 8 figure