The error occurs as SQL Server database files and backups are not backward compatible restricting restore of database created from higher SQL Server version to lower version. Below are some of the steps to migrate the SQL Server Database from higher version to lower version:
1. Use Generate Scripts wizard of SQL Server Management Studio in Higher version
In this step, we will first script the schema of the desired Database on SQL Server 2012 instance to migrate the database to SQL Server 2008 R2 using Generate Scripts wizard of the SQL Server Management Studio.
There’s no easy way to do this; database upgrades are generally a one-way action.