Here are the corrections for each sentence:

1. The weather today is not as hot as it was yesterday.
2. How long do you go to the movies? Twice a month. (No correction needed.)
3. My mother doesn’t like rock music, and I don’t either.
4. Your violin is the same as the one I just bought. (Alternatively: Your violin is the same as mine.)
5. She has gone to visit Susan. She’ll be back tomorrow.
6. I haven’t done any volunteer work lately.
7. We should encourage people to recycle glass, cans, plastic, and paper.
8. Did you live in Vancouver when you were young?