The version on the device is compatible with version 3.5 on the desktop, but the Windows Phone version of the database engine has some of the features from version 4.0, namely enhanced encryption and support for OFFSET and FETCH paging syntax.

http://stackoverflow.com/questions/16358820/which-version-of-sql-server-ce-does-wp-8-supports

http://stackoverflow.com/questions/16237674/wp8-sql-ce-4-0-database-deployment-error-an-attempt-was-made-to-load-a-program?rq=1

In short, you can only add v3.5 DB created on Deskto to project, v4.0 db will be generated in WP8.