Recently got a question regarding PowerShell installation hence this post took an existence.
How to Install PowerShell various versions
http://technet.microsoft.com/en-us/library/hh847837.aspx
Can we have more than one version of Powershell?
Yes, You can have multiple versions PowerShell.
How to switch between Powershell version?
ps:\>Powershell -version 4
ps:\>Powershell -version 3
ps:\>Powershell -version 2
Hope this simple post solve various doubts.
Happy Learning:-)