Reviews can only be deleted in the planning phase.You can only cancel or reject it after the planning phase by the owner or the admin account.
There are 2 ways to change the owner of the review:
1. You can change the log/pass of a user by the admin login(admin or your admin account name).Then you must to re-open the review (you can do that by the author account or the admin account) and change the author of the review.
2. The second way is doing all this steps by the admin account.