Regarding regression - from my point of view.
I think they get bored. We don't read aloud any more..... So many people see as regression I see as boredom. I try to see what next thing Edward is interested in and make resources available (including myself) for him to utilise to give him other ways of learning the new strength. I may be not even near his intelligence but I am his key to learn to communicate, they say asd kids use people as tools, but I think it is just their way of involving us in their lives, the more they do this the better they get at communication for everything.