  Seismic data obtained with the space photometric CoRoT and Kepler instruments
have led to a unprecendently precise characterization -- in terms of masses and
ages -- of a large sample of post main sequence stars (low mass subgiant and
red giants). The high quality of the collected seismic data and the subsequent
theoretical work for interpreting them brought up a series of issues which
revealed that our knowledge of the internal properties of red giant stars
remains quite limited. Two such important issues are discussed here, namely
mixing beyond the convective core of helium burning red giant stars and
evolution of internal angular momentum for post main sequence stars. This
includes how they were diagnosed and what are the resulting improvements in our
understanding regarding these issues (or rather how far we are from a proper
understanding and realistic modelling of the structure and evolution of post
main sequence stars).
