Maintaining your Exchange Servers with the latest updates is a best practice, for support, security, and stability reasons.
Testing Connectivity and DNS Changes with a Hosts File
How to use hosts files on client computers for Exchange Server testing and troubleshooting scenarios.
Installing Exchange Server 2013 Pre-Requisites on Windows Server 2012 or Windows Server 2012 R2
How to install the pre-requisites for Exchange Server 2013 on a Windows Server 2012 server.