with apple cider there is no citric acid.
i would think the large amount of citric acid would kill the yeast while it ferments. i am not positive, but with my experience with acids, it would seem that the yeast would not last long enouph to fermet the suger in lemonade into alcohol.
to me it would seem you would have to add the lemon flavor after fermentation or add the alcohol after makeing lemonade.
as i said i have no idea, i am just kicking around ideas but citric acid is pretty harsh on live organisms.