I think the most appropriate translation is "vero" (which works for negative as well as positive questions): "non ti è piaciuto, vero?" / "ti è piaciuto, vero?".
There are also other expressions; for instance you can also say "ti è piaciuto, no?". "No" should be used for positive questions, maybe is a bit more colloquial and (oddly) is less dubitative: they speaker really believes what he's asking for. "Vero", on the other hand, can also be used for rethorical questions "State scherzando, vero?" (Are you kidding?)
As I understand it, «qua» ("here") and «là» ("there") are used very generally. Without context, «qua» can mean anything like "on this desk," to "in this room," to "in this country." It is not very specific. It is the same thing for «là». On the other hand, «qui» ("here") and «lì» ("there") are very specific. For «qui», you are able to point with your finger on a paper for example and say "right here." It is the same thing for «lì». Therefore, I think you can say «Non è qui.» and «Non è qua.», depending on the situation. For example, let us say that I am looking for a paper in my office. If I just finished looking through a drawer, I can say «Non è qui.». Then, when I have searched the entire office and my boss asks where it is, I can say «Non lo so. Non è qua.».
On the whole, the differences are not too great. The only thing you really cannot do is point to a line in a document, for example, and say «qua».