Here are the completed questions and short answers based on the provided sentences:
Sentence: I've made popcorn.
Question: Have you ever made popcorn?
Answer: No, I haven't.
Sentence: I've never won a competition.
Question: Have you ever won a competition?
Answer: No, I haven't.
Sentence: My best friend has cooked at my house.
Question: Has your best friend ever cooked at your house?
Answer: Yes, he has.
Sentence: I've never drunk fresh lemonade.
Question: Have you ever drunk fresh lemonade?
Answer: No, I haven't.