After you perform the basic downgrade steps, finish the process by handling residual tasks.
sp_audit "exec_procedure", "all", "sp_addlogin", "on"
After you run installmaster, installmodel, installcommit, installsecurity, installhasvss, installjsdb, and installmsgsvss on your downgraded server, return system stored procedures to their earlier form. New stored procedures introduced in releases subsequent to the downgraded server are not removed.
isql -Usa -P <sa_password> -S <server_name> -i <restore_msgs.ebf>