How to upgrade SQL server 2008 to 2012?

You are done with the in-place upgrade, but were not connecting to SQL Server 2012 using SSMS 2008R2 and SSMS 2012.

Using T-SQL - will give you the correct version:

SELECT SERVERPROPERTY ('MachineName') AS PhysicalMachineName, SERVERPROPERTY ('ServerName') AS SQLServerName, SERVERPROPERTY ('Edition') AS ServerEdition, CAST(SUBSTRING(@@Version,charindex('SQL',@@version, 1),15) AS VARCHAR(255)) + ' + ' + CAST (SERVERPROPERTY ('productlevel')AS VARCHAR (50)) + ' + (Build' + CAST (SERVERPROPERTY ('ProductVersion') AS VARCHAR (50)) +')' AS ProductVersion, RIGHT(@@version, (Len(@@Version)-charindex('Windows',@@version, 1))+1) AS [O.S.], SERVERPROPERTY ('Collation') AS CollationHere is the best practice to upgrade SQL server 2008 to 2012:

• Before upgrade - run the above script to get the version and after upgrade, run it to make sure that you are on correct right version.
  
• Always use the latest version of SSMS (regardless of SQL Server version).