I was wondering if I could ask a question on meta whether some question is on the site or not. I'm asking this since sometimes one might ask a duplicate question which he/she searched for and didn't find due to different wording or format.
Duplicates can be useful. It is quite possible for two people to ask essentially the same question using different terms. When this happens on main, and the duplicate is recognized, the questions get linked. In the future, users searching for either term will find the answer, because the search will hit either the original question, or its duplicate.
There is no "economy" achieved by creating a meta question looking for duplicates; even if someone points out a duplicate, you have already created an extra thread. And this one will not be as useful as a duplicate on main, because people searching the main site will not find the meta thread. Of course, if there is no duplicate, then the thread is a waste of time for everyone involved.
Conclusion: if you did not find an answer by searching the main site, you should ask your question there.