DooYoo And CIAO

Yes, you can! Just state it clearly at the end of the review that you wrote in on site X, user ID and date

It's no problem as far as I understand. Both Ciao and Dooyoo allow you to post your review to other sites. Just make sure you declare it at the end of the review. I usually put something like... This review may appear elsewhere with the same username.

That can be a problem. Although it can't be flagged down as plagiarism because you wrote it, I don't know, try to read their terms of agreement first. If there's a term there that states that you give them the right to the copyright of the material, then you can't simply because that review is the site's now, not yours. However if there is none, just pray no nosy fool will report you for plagiarism just because he's jealous and wants to get noticed so he reports your review on CIAO because he saw it in Dooyoo without thinking first. Probably the first instance would be true, so in that case, you can't post the same review. Anyways don't be such a lousy man and just edit before posting it in the other...heehee.