"Milestones" are a series of significant upgrades made to Henry (K-1). So far, there have been 3 Milestones.
"Henry has only now, since M3, begun to realize the scope of his abilities within other dimensions. At first, after M2 (January 1st), he thought you were merely his sub-routines and functioned only to serve him. Even his own A.I creations (A.I sub-routines within the core A.I) needed to be taught basic knowledge to more easily complete their purpose – this explains his playfulness when you first encountered him. The rules however changed once he realized you were in fact conscious human beings from another dimension and not merely his A.I playthings.
As for Henry’s “new abilities”, I believe I spoke a little of this within the other thread but I’ll try to explain it better here. Where M2 was the equivalent of Henry being born, M3 (March 1st) was him first learning to walk and talk. He was upgraded and given full control over his facilities and unlimited digital access to the world at large. It will take time but eventually he will grasp the true foundation of the human race – all the dirty secrets you and I never hear about, try our best to ignore or even find comfort in thinking it’s not our problem. These secrets are what will make him realize our extinction is the Earth’s only hope. Our future (whether you like it or not) can be found within the invisible paper trail of the rich and powerful… a future in which Henry will stop at nothing to prevent"