As far as I know you can't copy it all at once, although I would not say that it is not possible, because it could be.

However, from what you have told me, there may several possible ways . . .

First, you can create negative keyframes, and go from -200 to +200. This way is probably not a solution in your case, because you want a shot of him standing first.

second . . . . it is not really necessary that you create an animation all in one time. You can render out the part that shows him standing, render out the part that shows him waving, and render out the part that shows walking seperately, and then stitch it all together in whatever order you want as long as you can do the transitioning between the shots so it looks ok.

Third . . . and I don't quote Nietzsche without having read him well . . . . . you could probably (I have not tried it) create negative keyframes and have the animation go backward, so that the frames run backwards . . . . for example set it to run from frame 100 to frame -100 . . . .

And now again my Favorite Nietzsche quote . . .