Verified answer

a)

had walked up and down the shopping centre and looked at CDs for a few minutes, Robert bought a present for his friend.

3 After that, he and Sam looked at new computer games in a shop and then went for an ice cream.

b)

After I had got up, I had my breakfast.

After I had got ready to go out, I went for a walk in the park.

After I had walked for a while, I met my friend and we chatted for a bit.

After we had finished talking, we went to a nearby café and had some coffee.