Why is the Windows Features window showing PowerShell 2.0 installed?
PowerShell v3 is build into Windows 8, you can not add/ remove it.
v2 is different story - it's optional, system will operate normally without it, so you can disable/ enable it. To use it - you need to run powershell.exe with parameter -version 2 - it should be first parameter on the list for it to work.