How can you use Q&A to gain good Karma and also aid to realize liberation How can you use Q&amp;A to:


effectively and efficiently create good Karma, and
also use it as an aid to reach the final Buddhist goal


Also what Suttas and literature, cover these topics?
How can you use Q&amp;A to gain good Karma and also aid to realize liberation?

By reflecting on a few principles when asking &amp; answering:  

Asking &amp; Answering

Notice in what category does the question lie in:


  "There are these four ways of answering questions. Which four? There
  are questions that should be answered categorically [straightforwardly
  yes, no, this, that]. There are questions that should be answered with
  an analytical (qualified) answer [defining or redefining the terms].
  There are questions that should be answered with a counter-question.
  There are questions that should be put aside. These are the four ways
  of answering questions."
  -AN 4.42, Questions


And if the answers given are appropriate to that kind of question:


  "Monks, it's through his way of participating in a discussion that a
  person can be known as fit to talk with or unfit to talk with. If a
  person, when asked a question, doesn't give a categorical answer to a
  question deserving a categorical answer, doesn't give an analytical
  (qualified) answer to a question deserving an analytical answer,
  doesn't give a counter-question to a question deserving a
  counter-question, doesn't put aside a question deserving to be put
  aside, then — that being the case — he is a person unfit to talk with.
  But if a person, when asked a question, gives a categorical answer to
  a question deserving a categorical answer, gives an analytical answer
  to a question deserving an analytical answer, gives a counter-question
  to a question deserving a counter-question, and puts aside a question
  deserving to be put aside, then — that being the case — he is a person
  fit to talk with.
  -AN 3.67, Topics for Discussion (I recommend reading the entire discourse since it has additional valuable advice. You might also want to read Bhikkhu Bodhi's translation)


Notice that not all questions deserve an answer since they are off-topic or have implicit assumptions which makes them so. Here's an article regarding this kind of questions which I think is worth reading.  

Asking  

When asking, be aware of the motive behind your question:


  Ven. Sariputta said: "All those who ask questions of another do so
  from any one of five motivations. Which five?
  
  "One asks a question of another through stupidity &amp; bewilderment. One
  asks a question of another through evil desires &amp; overwhelmed with
  greed. One asks a question of another through contempt. One asks a
  question of another when desiring knowledge. Or one asks a question
  with this thought, 'If, when asked, he answers correctly, well &amp;
  good. If not, then I will answer correctly [for him].'
  
  "All those who ask questions of another do so from any one of these
  five motivations. And as for me, when I ask a question of another,
  it's with this thought: 'If, when asked, he answers correctly, well &amp;
  good. If not, then I will answer correctly [for him].'
  -AN 5.165, On Asking Questions  




For a broader and more in-depth understanding of this topic, I recommend reading the related discourses which are mentioned at the end of the discourses linked above and a brilliant book written by Thanissaro Bhikkhu named Skill in Questions: How the Buddha Taught. It has many examples of Q&amp;A's that fit the above categories.