inetmgr / machine key question

Running IIS on Windows 2012 and have some questions about the Machine Key applet in Inetmgr.  When using InetMgr to set the validation / decryption keys for .NET. where does the key value get stored?  We have multiple .NET framework apps on our IIS box. Does this decryption key value apply to .NET 4.5, .NET 2.0?  .NET 4.5 32 bit?  .NET 2.0 64bit?  How does IIS know where to store this value?

thanks