I'm currently running TFS 2013 on one Windows Server 2012 box and TFS Build 2012 Update 4 on another box. My question is if I upgrade my TFS Build Server box to utilize TFS Build 2015, will I need to upgrade my TFS 2013 Server as well?
Also, what about the opposite? Can I upgrade my TFS 2013 server to TFS 2015 and still use my existing TFS Build 2012 Server which is using web deploy to build and publish to various other servers on our network?