I have a problem with this:
1. "He knows this man./How long has he known this man?"
2. "He has a car./How long has he had a car?"
In both these examples we use "How long+Present Perfect" to ask about the continuity. But I do not undestand why we cannot use the same structure with "have got":
"He has got a car./How long has he got a car?" (I think it's wrong)
I think that "How long HAS HE HAD a car.'" will be correct, but then why can't I use "has got" as it is also Present Perfect?
In fact, the question, according to your examples would be:
3. * "He has got a car./ How long has he had got a car?" This is obviously wrong. You need to form the question according to the meaning, not based on this idiomatic form with 'got'.
Note also that you can't use this construction with the present perfect:
4. * "I've received my degree./"How long have you [had] received your degree?" Wrong!
5. * "He has arrived./ "How long has he [had] arrived?" Wrong.