The more concentrated HCl is, the more ions in the solution are (bigger conductivity). You said that pure HCl can't be obtained, so the conductivity would increase to a level, then after increasing the concentration of HCl it should start to decrease (because there are less ions) and then it remains at a point (because pure HCl can't be obtained). Correct?
Why pure HCl doesn't exist? If there is no water, HCl won't dissociate and I thought that it should exist. But HCl is initially a gass, so it needs to be dissolved in water to make the acid. Is this the reason?