prayers after death

hi sir,
what a peous or awliya do after death in graves?
can he pray namaz or go for hajj?
i heard , Awliya karaam (dead awliya)are going madina( masjid_e_nabvi) every friday night to prophet(pbuh). is that right for awliya karaam to travel from thier graves to hajj and masjid-e-nabvi.