1. By the age of 10, I had learned to ride a bike.
2. By the age of 10, I had made a lot of friends.
3. By the age of 10, I had visited my grandparents every summer.
4. By the age of 10, I hadn't traveled abroad.
5. By the age of 10, I hadn't read "Harry Potter".
Ответ: см. выше