A: Yes. Installing Windows PowerShell 3.0 doesn't remove 2.0 if it was already installed. However, if PowerShell 1.0 was installed, then the installation of PowerShell 2.0 or 3.0 will remove the 1.0 installation.
If 2.0 and 3.0 are installed on the same box, then launching Powershell.exe will start 3.0. To start 2.0, run
powershell -version 2
To quick show if you are runing 2.0 or 3.0, use
To learn more about PowerShell, see our PowerShell 101 Series, or see "Top 10 Active Directory Tasks Solved with PowerShell."