I want to find out files under a given directory which have been updated most. Is there any command which can display this info? Or is there any way to get max version count for a given file, so I can write some script to get this info from all and then sort desc.
Do you mean changed the most number of times, or undergone the most code chrun?
Either way - looking at the report data might be the easiest option for you. Take a look at the following blog post I did explaining how to use Excel for looking at TFS data that uses churn as an example allowing you to drill down into folders and files - but you should be able to get the data that you are looking for.