Okay so. There are a few flaws to your cat that make it impossible to work.

1. Realistically, if a cat were to be born like this, it would make sense they didn't know how to do anything. Your cat would be as good as still-born because as a kitten, he wouldn't have nursed, nor would he have been able to get to the milk if -- assuming -- he had siblings. He would've been shoved to the side unless mom was gracious enough to keep him and attempt to help. Even if that was the case, he wouldn't have been able to develop the correct skills in general. He wouldn't be able to move therefore lack the muscles to attempt to and when a cat (or any animal) puts weight on their internals for too long, it'll damage them resulting in death. Briarlights situation for example. Although as you made clear, their situation was worse.
2. Even if they were to make it through kithood, the clans wouldn't ever allow them to train. They'd be elders den or medicine cat den bound their entire life. They'd be too much of a liability if they were allowed to train to be a warrior or a medicine cat. It'd be much simplier to just keep them in camp and have cats take turns keeping watch/take care of them. On top of that, even if mentors were alternated their whole life to train him basic needs, that's one less cat to train a different apprentice that could benefit the clan. It wouldn't be worth the clans time.
3. You can have them have whatever mental illness you want as long as it's appropriate, but realistically, this feline could not physically function in the clan resulting in them being just another mouth to have to feed. The clan is capable of caring for them, but in most cases, the cat would be disowned.

@Okapi @Crow