Hi Paco,
Here are some comments.
(1) (x) I knew her five years ago.
This is wrong. "Five years ago" is a point-time adverbial and so it can't go with a stative verb "know". It sounds OK to me. My understanding is that you have lost contact with her, thus you don't know her now, you don't have a relationship now..
(2) (o) I've known her for five years.
This is right. It means we got acquainted with each other five years ago and still now we keep an intimate relationship. Sounds fine. The term 'intimate relationship' is one you need to be careful with, though!
(3) (o) I knew her for five years, but we lost touch two years ago.
This is right. As the state of my knowing her is now a past event, we can describe it in simple past tense. Yes. It could be rewritten like below.
"I had known her for five years, but we lost touch two years ago." Yes.
You also say that ...I thought previously "know someone" could be a dynamic verb Well, I know you are interested in the history of language, its development and archaic expressions. So, I want to point out an archaic usage of 'know someone' that is extremely dynamic, at least if you do it right.
'Tom went into Mary's bedroom and knew her' is an archaic way of saying they had sex. The Christian Bible, in the Old Testament, is full of this usage. It's not even that long ago that people spoke of 'carnal knowledge'. In Britain, people would be (perhaps still are) charged with the crime of 'unlawful carnal knowledge' (of a minor, for example, to be more serious).
So, as I said, 'to know' has a dynamic history!
It makes you think again about some of the well-known sayings about knowledge, eg
'A little knowledge is a dangerous thing'
or 'It's not what you know, it's who you know'.
Anyway, good luck with your pursuit of knowledge.
Best wishes, Clive