  We report on transport measurements of dual-gated, single-layer graphene
devices in the quantum Hall regime, allowing for independent control of the
filling factors in adjoining regions. Progress in device quality allows us to
study scattering between edge states when the four-fold degeneracy of the
Landau level is lifted by electron correlations, causing edge states to be spin
and/or valley polarized. In this new regime, we observe a dramatic departure
from the equilibration seen in more disordered devices: edge states with
opposite spins propagate without mixing. As a result, the degree of
equilibration inferred from transport can reveal the spin polarization of the
ground state at each filling factor. In particular, the first Landau level is
shown to be spin-polarized at half-filling, providing an independent
confirmation of a conclusion of Ref.[1]. The conductance in the bipolar regime
is strongly suppressed, indicating that co-propagating edge states, even with
the same spin, do not equilibrate along PN interfaces. We attribute this
behavior to the formation of an insulating nu=0 stripe at the PN interface.
