Salam alaikum sister:
Age of 4 would be difficult to determine I think.
Having a learning disability is used more when discussing a child that will take an extremely long time to learn the basics. This child will struggle constantly trying to learn. This would be very noticable I would think, even at a very young age. However, with a determined teacher and parents, they will eventually learn. A learning difficulty means there are areas where there child has problems, but will eventually learn how to overcome the difficulty to make learning somewhat easier. It will never be super easy and they will always have to work hard, but they will learn.
My son was tested and scored above average to average in all areas EXCEPT the ability to focus, where he almost fell off the charts!! Basically, my son can't stay focused enough to keep things clear. It would be like words and colours moving over the screen and trying to read it. The poor kid is like me....he as the attention span of a gnat.
However, one on one is perfectly fine, visual cues help a lot. These children are usually very good playing video games or using the pc because these are visual and hands on.
At age 4, you can try little things like giving him a list of 3 things to do. "Go to your room, get the red block and put it on the kitchen counter." See if the child can do that. My son would never get all 3 without a reminder. Bless his heart, at 4 years old, he MIGHT remember the red block IF he made to his room without something else grabbing his attention.
Try to get him to put an easy puzzle together and watch to see if he is easily distracted.
You'll have a much better idea once the child is in school and you see how he/she progresses.
Wasalam,
Hana