...
Keep in mind when testing in either the backup or testing environment, all changes that are made should be manually copied to production. Since Production gets copied to the Backup every night, long-term testing is performed on the Testing environment to prevent your changes from getting overwritten.
The test environment gets overwritten with the production data about one to two weeks before the next release (to be able to test with up-to-date production data). Keep this in mind when planning or doing longer-term work on the test environment. There are also no guarantees on how often the test environment gets overwritten with the most recent production data.