What are the effects of separation at hypersonic rarefied flows?
Hypersonic rarified conditions means you're almost in space.
You are asking can you stall? Maybe the first question should be can you fly?
Correct me if I'm wrong but it seems that you are trying to apply a real life exemple to a totally different area of flight. The stall you are referring to happens in transonic flight when the shock wave appearing on the extrados forces the flow to detach.
In subsonic/transonic flight lift is generated through an acceleration of the flow around the extrados resulting in a pressure loss on the succion side of your wing. If the flow detach you're losing this acceleration effect of the flow following the surface of the wing and thus you lose lift.
In supersonic flight the shock waves starts attached to the leading edge of the wing. The shock deviates instantly the flow and the more the flow needs to be deviated the stronger the shock and the more pressure increases. Lift is generated through the difference of deviation in the flow betew intrados and extrados resulting in pressure difference on both side. The boundary layers here doesn't play a huge role and I've never heard of supersonic flight stall.
In hypersonic rarefied condition the shock detach from the body and you have very high temps, and complexe chemistry hapenning inside the layer between the shock and your surface thus making the flow hard to simulate. First of all you don't really use wings in this mixture of high energetic particles so speaking of stall doesn't make sens. Then lift is mostly done the same way as in supersonic, through the differential increase of pressure being the shock but the chemistry between the few molecules of air can create weird stuff resulting for exemple in asymmetrical lift on a surface for very complexe not always well known reason.