4 year old says I don’t know to EVERYTHING

i need help guys. My son turned 4 last month, he’s a very smart kid and overall is pretty good and on track In his learning. But he says “I don’t know” to quite literally everything. I’ve tried so many different ways to re word things, to help him understand things because I thought maybe I was asking him things in ways he didn’t understand. Here are a few examples..

Today he put pretzels in the litter box, when I asked why, he said I don’t know. I asked if he was trying to play, or if he was trying to empty out the container of pretzels, etc. every question was met with “I don’t know”

He took all the towels out of the bathroom and put them in the dirty clothes so I had a little talk with him and asked if he put them there because he thought they were dirty.. same answer.

He’ll hit his sister, and will say he doesn’t know why.

The list goes on and on and on. I’m always trying to help him through his emotions and impulses, trying to communicate with him in a way he will understand.. but it’s always the same answers. We have taken him to the doctor to be evaluated for various things because on top of him always saying he doesn’t know, he will not hold eye contact, if he does something mean and I pretend to be really hurt to get him to understand, he laughs. He doesn’t understand boundaries at all, I know he’s 4 so I don’t expect too much from him but for example, I have an iPad that I let my kids watch a little bit of tv a day and every single day I reenforce the boundary that he can not touch it. He will say he understands and will promise not to touch it and then he always does. A week ago, not even 5 minutes after talking to him about it, he picks it up and drops it. So we had a talk about it and the consequence was for him to not watch tv on it for a while. Today he kept asking and begging, telling me for over an hour that he would not touch it. My husband said he seemed like it really got through to him.. and within 5 minutes, he was pushing buttons and trying to take it to his room. When I took it away and tried to explain, he screamed at me saying he hates me and that I am always mean to him 😕

I’m not sure where all of this is coming from. Our other kids 5 and 6 are not like that at all. All the doctors have said he’s fine, and I’ve changed the way we parent but it still doesn’t work! Does anyone else have kids like this that could share what worked for them?

At the end of the day I know he’s young and I’m trying to be as patient as possible, I’ve just never had to deal with this so it’s very frustrating