  Traditionally, low-pT sector is used to infer the features of initial stages
before QGP thermalization. On the other hand, recently acquired wealth of
high-pT experimental data paves the way to utilize the high-pT particles energy
loss in exploring the initial stages. We here study how four different commonly
considered initial-stage scenarios which have the same temperature profile
after, but differ in the 'temperature' profile before thermalization affect
predictions of high-pT RAA and v2 observables. Contrary to common expectations,
we obtain that high-pT v2 is insensitive to the initial stages of medium
evolution, being unable to discriminate between different conditions. On the
other hand, RAA is sensitive to these conditions, however, within the current
errorbars, the sensitivity is not sufficient to distinguish between different
initial stages. Moreover, we also reconsider the validity of widely-used
procedure of fitting the energy loss parameters, individually for different
initial-stage cases, to reproduce the experimentally observed RAA. We here find
that previously reported sensitivity of v2 to different initial states is
mainly a consequence of the RAA fitting procedure, which may lead to incorrect
conclusions. On the other hand, if a global property, in particular the same
average temperature, is imposed to tested temperature profiles, high
sensitivity of high-pT v2 is again obtained. We however show that this
sensitivity would not be a consequence of differences in initial, but rather
final, stages. Consequently, the simultaneous study of high-pT RAA and v2, with
consistent energy loss parametrization and stringently controlled temperature
profiles, is necessary to assess sensitivity of different variables to
differences in initial and final stages.
