1. You can force hide it by script. But it is not recommended since the entire idea with this can of File manager is dual panel. Active panel is by default source, and the Inactive panel is Target and a lot feature depends on that. So even if you hide it it is still there, So you might do things to it without knowing.
2. Only the QuickLaunchBar is current customizable. You can add external programs and UserDefinedCommands there.