SQL server 2012 Feature Upgrade failed

I had my SQL 2008 R2 Enterprise Edition and I was trying to upgrade it to SQL 2012 Standard version which is not allowed

Unsupported Scenarios

 ·  Cross-version instances of SQL Server 2012 are not supported. Version numbers of the Database Engine, Analysis Services, and Reporting Services components must be the same in an instance of SQL Server 2012.

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·         ·  Cross-platform upgrade is not supported. You cannot upgrade a 32-bit instance of SQL Server to native 64-bit using SQL Server Setup. However, you can back up or detach databases from a 32-bit instance of SQL Server, and then restore or attach them to a new instance of SQL Server (64-bit) if the databases are not published in replication. You must re-create any logins and other user objects in master, msdb, and model system databases.

·        ·   You cannot add new features during the upgrade of your existing instance of SQL Server. After you upgrade an instance of SQL Server to SQL Server 2012, you can add features by using the SQL Server 2012 Setup. For more information, see Add Features to an Instance of SQL Server 2012 (Setup).

·     ·    Failover Clusters are not supported in the WOW mode. If you currently have SQL Server 2005, or SQL Server 2008, or SQL Server 2008 R2 failover clusters on the 32-bit subsystem (WOW64), upgrade of the failover cluster to SQL Server 2012 is not supported

·     ·  Upgrade from SQL Server 2005 Evaluation, SQL Server 2008 Evaluation, and SQL Server 2008 R2 Evaluation to SQL Server 2012 is not supported.

Reference : http://msdn.microsoft.com/en-us/library/ms143393(v=sql.110).aspx