If 4 did not exist, then you would be using a base-4 quarternary numbering system (which is able to use the numbers 0,1,2,3)

The system will be similar to how our base 10 numbers work, but instead of counting to 9 before adding a trailing zero and becoming 10, you would count to 3. So 2 plus 2 would roll past 3, and equal 10.

You’ve inadvertently hit on the beginnings of an apparent paradox to do with the relationship between numbers and the counting numbers

Suppose the largest number you can have is X and the smallest number you can have is -Y. Then between -Y and X, you can count X+Y numbers which is clearly larger than X. But X is the largest possible number so X+Y doesn’t exist.