There is ONE mistake in each sentence and correct it

Question 2. There is ONE mistake in each sentence and correct it.
1. It was an unique opportunity for her to join the games. => ________________________
2. He spends most of his free time looking up his dog. It is ill. => ________________________
3. He can do this task much more easier than the others. => ________________________
4. I find it useful doing DIY. Let’s do it when we have free time. => ________________________