You need to Uninstall SQL Server 2014 CTP1 to install SQL Server 2014 RTM

SQL server 2014 RTM will be available from April 1, 2014. It's time to take out SQL Server CTP1. You really need to take out CTP1 if you have installed it as these are the general restrictions:

• Upgrading from SQL Server 2014 CTP 1 to SQL Server 2014 RTM is NOT supported.
• Installing SQL Server 2014 CTP 1 side-by-side with SQL Server 2014 RTM is NOT supported.
• Attaching or restoring a SQL Server 2014 CTP 1 database to SQL Server 2014 RTM is NOT supported.

However upgrading from CTP2 is supported but degrading to CTP2 from RTM is not.

According to the same source the following upgrades are supported as seen in the referenced link:

• Attach a SQL Server 2014 CTP 2 database to an instance of SQL Server 2014 RTM.

• Restore a database backup taken on SQL Server 2014 CTP 2 to an instance of SQL Server 2014 RTM.
• In-place upgrade to SQL Server 2014 RTM.
• Rolling upgrade to SQL Server 2014 RTM. You are required to switch to manual failover mode before initiating the rolling upgrade. Please refer to Upgrade and Update of Availability Group Servers with Minimal Downtime and Data Loss for details.
• Data collected by Transaction Performance Collection Sets installed in SQL Server 2014 CTP 2 cannot be viewed through SQL Server Management Studio in SQL Server 2014 RTM, and vice versa. Use SQL Server Management Studio in SQL Server 2014 CTP 2 to view data collected by the Collection Set installed in SQL Server 2014 CTP 2, and use SQL Server Management Studio in SQL Server 2014 RTM to view data collected by the Collection Set installed in SQL Server 2014 RTM.

Watch for a detailed post on uninstalling SQL Server 2014 CTP1 here:
http://hodentekMSSS.blogspot.com