If you think you understand what's needed to make a Human Level AI, then you shouldn't need a five step plan. (at least not with these steps) If you expect to learn anything important from the toddler stage that will let you move towards the adult stage, then you already know you don't understand the problem.

From: http://opencog.org/faq/

Q: What’s the Secret Sauce?

In a phrase: cognitive synergy.

The insight here is that many parts need to work together.

Setting the "toddler" target makes it seem like you're breaking the problem down into a more manageable chunk, but it's actually at least as large as the original problem. The village idiot and Einstein are very close together on the spectrum that includes Dogs, chimps, and superhuman AI, and I think a 4 year old might be above the village idiot. If you can do that, just finish it.

4-year old level problem solving ability at 4-year old speeds is a severely anthropomorphic prediction of a designs abilities. If you could do that, why not crank up the speed (at least) and get a thing that can do real work. Perhaps still conceptually simple by adult standards, but way ahead of current bots. You could almost certainly get through very complex problems if you could give instructions to an immortal toddler.

There is no such thing as a digital toddler that is not a recompile away from superhuman AI. I'm guessing that this plan stems from some kind of humility, or not wanting to fail. It feels easier to make what you think is a weak intellect. Given the existing virtual dog, it might feel like they're making progress. It would certainly be possible to make a toddler that is increasingly convincing as a toddler.

This is wasting a bunch of effort on Machine vision, NLP, and dancing robots, which I think do not feed into general intelligence. If you're convinced friendliness isn't important, and you need a hard sample problem for your AI, pick cancer, not cyberchat.