If you are selecting 'Restore the database using existing database files', then you need to make sure that the existing DB files should be associated with the same SnapCenter backup snapshot that you are selecting to restore from. If not, Restore will fail with an appropriate error pointing to the above requirement.
If you wish to have a fresh latest copy of your production DB, select the latest backup with the option 'Restore the database to an alternate host', choose the same server/instance and give new target directory paths for the copy Database. This will basically do a 'Restore to alternate path' under the same instance.