Can I reuse a recommendation letter that was given to me a year ago for PhD applications now? I took a recommendation letter from one of my Professor last year and I want to apply for a PhD position now.Is it OK if I send that recommendation letter or should I ask for a new one?
Would you send a CV that's a year old?

You have hopefully been doing something in the time between when your professor wrote the letter and now. Your reference letter should reflect that. If you can, ask them for a new one, otherwise find someone who you've been working with more recently to ask.