Why does your 4 year old know?

[LifesTooShortYOLO]

My DS is 4 years and 2 months and can count to 20, he knows many phonic letters but not the whole alphabet.
He gets confused when we talk about counting backwards from 20.
He knows rhyming sounds and a for Apple b for book etc.
Just curious as to what is expected at this age of 4 year olds?

There will be children who know more, and children who know less. Your child sounds completely on track to me though.

What CP2701 says.

As previous posters have said - it sounds about average, I would expect most 4 year olds to be able to do the things you listed (i.e. it would not be uncommon for a 4.5YR old to be able to read short sentences and do simple one digit summation)

If you're worried about him starting school then self care knowledge is useful too. Not all kids will be able to do this but
Can he put his shoes on correctly? (Left/right) Can he wipe his bum?
Get changed ?
Put his coat on including zip?
Does he know his surname?
Can he use cutlery to eat his lunch?
And so on

The reading and writing is very variable
Your son is in the normal range - there will be kids who know less and kids who know more