Time with AT, IN & ON

Choose the CORRECT sentence:
1. The film starts at 3pm - don't be late!
2. The film starts on 3pm - don't be late!
3. The film starts in 3pm - don't be late!
Choose the CORRECT sentence:
1. I'll see you on Sunday then!
2. I'll see you at Sunday then!
3. I'll see you in Sunday then!
Choose the CORRECT sentence:
1. Let's have a picnic in the afternoon.
2. Let's have a picnic on the afternoon.
3. Let's have a picnic at the afternoon.