Can we restore SQL Server 2008 database to SQL Server 2005?

No we can't restore it. SQL Server is not allowing the restore of higher version databases to a lower version. It is not possible to restore a database from a backup of a newer version to older version as database backups are not backward compatible.

You can do below workaround to transfer higher version database to lower version.

1. Generate database script. Right Click database -> Tasks -> Generate Scripts



2. Execute the script on the lower version server and it will create the database and its objects

3. Transfer data between these two databases using DTS/SSIS