Why wasn't "I have known him since I was small" accepted?
A very good question! I have reported it.
Me too. Disappointed. I lost a heart for that.
In the U.S. small and little are interchangeable in this context
Also in UK
The narrator speaks it, "pequena"
I thought so too. And since it was a female voice...
Why is the first part before the since not in present tense ... In the portuguese sentence it seems like it is present until desde ...
The Portuguese present tense with words like "desde" translates the English present perfect or present perfect continuous. There are number of discussions about this feature, for example, see my comment here:
Can "que" be omitted?
No, it is mandatory in Portuguese.
I know him should be accepted because I'm talking now, in other word at the present time which is the form in Italian and Spanish as well
But not in English. You are talking about the period you have known him for, which is in the past.