Yes, well. There's a lot of things that are gramatically correct in portuguese but we don't use on daily conversation, haha. I'm just answering with what is usual.
It's like when I was learning english. For example: no one even thought of mentioning the existence of thee/thy/thou/thine. I found out on my own years later.
So I guess you could talk like this, but people would find it weird, haha.
Both mean the same thing and they are both understandable. The last one is incorrect, because when it comes to grammar you can't finish a phrase with a pronoun. Although I must say it is very colloquial and people say that all the time. In other words...you can say that but not write (in a test, for exemple) :)
I think magicbeans is discussing Brazilian Portuguese (I could be wrong), whereas I am wondering whether the use differs in European Portuguese. I know "a" and "o" are used for "it" in European Portuguese, I am just not sure whether this would also be the case when it is used with conheçer.