  We examine the structure, propagation and expansion of the shock associated
with the 2012 July 23 extreme coronal mass ejection (CME). Characteristics of
the shock determined from multi-point imaging observations are compared to in
situ measurements at different locations and a complex radio type II burst,
which according to our definition has multiple branches that may not all be
fundamental-harmonic related. The white-light shock signature can be modeled
reasonably well by a spherical structure and was expanding backward even on the
opposite side of the Sun. The expansion of the shock, which was roughly
self-similar after the first $\sim$1.5 hours from launch, largely dominated
over the translation of the shock center for the time period of interest. Our
study also suggests a bow-shock morphology around the nose at later times due
to the outward motion in combination with the expansion of the ejecta. The
shock decayed and failed to reach Mercury in the backward direction and STEREO
B and Venus in the lateral directions, as indicated by the imaging and in situ
observations. The shock in the nose direction, however, may persist to the far
outer heliosphere, with predicted impact on Dawn around 06 UT on July 25 and on
Jupiter around 23:30 UT on July 27 by an MHD model. The type II burst shows
properties generally consistent with the spatial/temporal variations of the
shock deduced from imaging and in situ observations. In particular, the
low-frequency bands agree well with the in situ measurements of a very low
density ahead of the shock at STEREO A.
