Here are the answers and explanations next to those:
1. I saw the twins in town last week. (specific time in the past)
2. Have you ever met her brother? (experience in the past)
3. Where were you last weekend? (about specific time in the past)
4. Have you seen Kathleen? (experience in the past)
5. We didn’t go on holiday last year.
6. I love clothes. I’ve bought a lot this year. (Thing still happens until the time of talking)
7. What did you do last weekend?
8. Dad has repaired the car, you can use it now. (The action has just finished and the result affects the present)
9. Agatha Christie lived from 1890 to 1976.
10. Granny still hasn’t found her glasses. (Thing started in the past and continues to the present)
11. Where did you buy your laptop? (Finished actions)
12. Oh! You’ve painted the kitchen, I like the color. (The result affects the moment of talking)
13. What time did you get home last night?
14. Emma! Your letter has arrived at last!
15. The weather has been good all week. (Thing happened in the period of time from past to the present)
16. I finished work early yesterday.
17. Sue’s not here, she’s gone out. (The result affects the present)
18. The weather wasn’t very good last week.
19. We’ve been to the cinema twice this month. (Experience)
20. Brian lived in England until the age of 14. (about specific period of time in the past)