To hide few tabs/modules for your organization, Goto Setup >Tab Settings >Organize Tabs >remove the unwanted tabs from the display and save the settings.
To hide tabs for Support Reps, you have to first create a New Profile or Edit the Standard Profile under Setup > Admin Settings > Profiles and remove the tabs that are not required. Now associate this Profile to a Support Agent. Goto Setup > Admin ...
Yes, you can re-order Tabs as per your organization requirement. Goto Setup >Tab Settings > Organize Tabs. Now, edit a particular module to change the display name of a tab. For more refer Tab Settings