Technically? Yes. Reality? Use a QA/TEST server
Yes. We are going to use a Test server.
Q1) Dashboards will work fine right, if i download from 8.2 and publish it to 9.3?
Q2)If i am upgrading the Server do i need to upgrade the Tableau desktop too?
You should not need to download and republish all the workbooks - they should still work after upgrading. However, downloading them and opening in a later version of Tableau Desktop and republishing them to the new version of Tableau Server will upgrade the workbook.
You do not "need" to upgrade Tableau Desktop (you can publish from an older version of Tableau Desktop to a newer version of Tableau Server) but you probably should to better utilize all the new features in the newer version of Tableau Server and to maximize compatibility between the users and the Tableau Server.
There is a great article that discusses desktop and server compatibility here: Desktop and Server Compatibility | Tableau Software
Hope this helps!
That's Wonderful!! So Are you saying that if i just upgrade the Tableau server and go to the old URL and still all the dashboards would be present??
Yes, that is accurate. I would highly suggest reading over and following the directions outlined in both the "Upgrading Tableau Server | Tableau Software" article as well as the "Pre-Upgrade Checklist | Tableau Software " (linked from within the upgrade doc). These two articles will guide you through the process. This is mentioned multiple times but PLEASE take a backup before doing anything and test the new version in a separate environment before wiping away the old one.
Good luck with your upgrade - open a case with Tech Support if you have any issues: http://www.tableau.com/support/request