As others have said he is 4.
I have had to re read your op a few times to make sure I am reading this right that he is 4 and not in year 4.
My DD was doing pretty much basic of basics at 4, I used to over hear other mothers muttering " At least he can hold a crayon properly now" at 2, and we were no where near any of that.
I supported my DD but did not stress out about her reading or writing.
She is now 6 and it was only when she was weeks off her 6th birthday that she literally has gone up stratospherically and I did think wow, this is amazing.
Everything clicked for her, and she is flying along.
I realised why European schools only start them at 6 or 7.
My DD was behind lots of others in nursery, who could write their own names and count to 20 and so on.
So please please do not write him off. Keep an eye on him but wait, support and keep things fun for him. He is so little. children are not robots all programmed to develop at the same time, they come to things in their own time. Albert Einstein wasn't supposed to have spoken till he was two or something.
Then, if after a few years you are worried, think about other avenues for himI heard fab interview once about man who told mother her daughter was a dancer and the academic environment was totally wrong for her, so she put her in a dance school, and now she is a top choreographer at the royal opera house or something. I am really sure I made sure he is 4 but if he is year for, apologies for long rampble.