Titles must not contain terms like "Demo" or any other type of wording that suggests the product was/is not available for sale or is not ready for the end consumer per music store guidelines.
Often times artists will create "Demo" versions of their tracks that they do not intend to release initially, and then at a later time wish to release that "Demo" version. While this content can certainly be released and distributed, the use of the wording "Demo" is not allowed by the music stores.