I believe that the limitations are hardware.
One of the reasons that organics like us are so efficient is that we have been created with an integrated system of input/export/imprint devices (so to speak).
Our mind doesn't work in 1's and 0's, it works in visual impressions and audio impressions and tactile impressions through impulses.
There is no computer in the world that could process all of that with 1's and 0's, let alone low watt power supplies.
So, by limiting the problem to language processing, we attempt to narrow it down to something we can handle.
The problem I see with #1 in your post is that of an "understandable form" to a computer that works off of a simple 1/0 switch in electricity.
In order to effectively create an efficient audio/visual input, it has to be integrated with multiple processors working simultaneously.
#2 is interesting... we want to program computers, but we have to teach children and allow them to learn as they grow through stages.
In the organic world, we have a system of learning that interacts with the environment we are part of and that can affect us.
In order for a computer to effectively analyze the input, it will have to be connected to the environment in which the input is coming from.
#3 is where things get even more complex, because the ammount if input in a single conversation can overwhelm a child's mind because they have no referent for the level of experience required to understand the information.
The reality is that a computer would have to rely on programming from a programmer that understands the world and then the computer would have to analyse and process the information received based on the interpretation of the programmer/s, not the interpretation of the computer itself.
So, there are a lot more issues involved with #1 and #2 and #3 because they cannot be developed seperately, but have to be considered a whole, which makes our current hardware inadequate.
These are just some thoughts... brainstorming... free association and all of that.
Just something to think about.
I am not started on the project yet, I am evaluating the viability of such a project.
If I do ever become involved in such a project, then I will definately make the progress available (open source and free to all)