나요?? Is usually ' can ' for question I mean. Can i use this sentence? 이 문장을 사용해도 되나요? Can i go now? 지금 가도 되나요? Can i have lunch? 점심 먹어도 되나요? If you want for the past tense, you have to put '었' Could i use it? 그것을 사용해도 됬었나요? Could i go at the time? 그때 가도 됬었나요? Could i have lunch? 점심 먹어도 됬었나요?

You can use ~었나요 for the past tense. 준비됐어요? = 준비됐나요? 준비됐어요 is contraction of 준비되었어요 준비됐나요 is contraction of 준비되었나요