A. What do you do in your free time?

I  watch TV.  ✔​

B. 1. I am 8 years old.

=> Another way: Your sentence is okay and this is another way of saying it. ​

She's eight.

2. 8years old

=> Another way: Your sentence is okay and this is another way of saying it. 

I'm eight.​

How old are you?✔​