Answer:

1-2.) They said the test would be difficult, but it was a piece of cake.

3-4.) Some of Rin‘s classmates think he is a mama’s boy because his mother walks him to school every day.

5-6.) My auntie has a heart of gold. She's the nicest person I know.

7-8.) No one knew about her earlier, but suddenly she is being seen as the dark horse with such amazing display of her abilities.

9-10.) He's a cheeky know-it-all, who gets away with anything because he's smart enough to deliver it with total innocence.