I just wanted to know if this reaction is once per player turn (meaning that I can play it both in my turn and in my opponent's) or if I have to wait a "complete" turn (meaning that if I'm the DS player I have to wait my new turn both if I played the reaction in my turn or in my opponent's)…Thanks

Note that there is no such term as "complete turn" that you mentioned in your question. There is only one definition for turn in Star Wars which is on page 13 in the Term Summary along with numerous other definitions.

Turn is an alternative term for player turn ; it describes
the six phases the active player must perform.

Thanks ! Yeah I imagined that because I couldn't find my meaning of "complete turn" anywhere on the rules but to be completely sure (since in both LOTR and AGOT the "turn" is a bit different) I wanted to ask you guys. Thank you for your answers.