DS2 has been able to imitate us for some time, but has never, to my knowledge, imitated or followed an instruction from another child. He just didn't seem to 'tune in' to children's voices - or unfamiliar adults either tbh.
Today I went on a school trip with him. On the way back he was sitting behind me with his friend. She tapped me on the shoulder and said ' See what DS2 can do'. I turned round to see them playing a game where she would touch her nose and say ' DS2, Simon says do this'. Ds2 was copying everything she did! I then got her to give him an instruction without doing the action herself, to see if he could understand the words alone and he did that too!
She then got very excited (totally egged on by me and started firing instructions at him, at which point he got very cross and put his hand over her mouth