Tear off menu by dragging caption

So, how can I restore the torn-off menus to non-torn-off state? That would be the big first step for me.

Open menu and press CTRL+T or right-click in the menu and remove the check mark from the "Tear Off Menu" menu item.

And then I'd need the option to disable tearing off to actually work!

You have to turn off the option:
TLB Settings->Menu->General->Tear Off menu by dragging caption