  A comprehensive study of the vortex phases and vortex dynamics is presented
for a recently discovered high-temperature superconductor YH$_6$ with T$_C$
(onset) of 215 K under pressure of 200 GPa.Thermal activation energy (U$_0$) is
derived in the framework of thermally activated flux flow (TAFF) theory. The
activation energy yields a power law dependence U$_0$ $\propto$ H$^\alpha$ on
magnetic field with a possible crossover at a field around 8-10 Tesla.
Furthermore, we have depicted the vortex phase transition from vortex-glass to
vortex-liquid state according to the vortex-glass theory. Finally, vortex phase
diagram is constructed for the first time for superhydrides. Very high
estimated values of flux flow barriers U$_0$(H) = 1.5-7*10$^4$ K together with
high crossover fields makes YH$_6$ a rather outstanding superconductor as
compared to most cuprates and iron-based systems. The Ginzburg number for
YH$_6$ Gi = 3-7*10$^{-3}$ indicates that thermal fluctuations are not so strong
and cannot broaden superconducting transitions in weak magnetic fields.
