To disable the database window, go to Tools | Startup, and uncheck the box
for:
Display Database Window
If you don't want the user to be able to activate it with F11 or get to the
Debug window with Ctrl+G, uncheck:
Use Access Special Keys
If you want to prevent the user bypassing this with the Shift key,
programmatically set the AllowBypassKey property.
Presumably you have split the database and created an MDE for the front end
so users cannot modify their forms/reports.
If you need more than that, you can use Access security, though that's
overkill for many applications.
Regarding disabling the nav buttons on the form, you can turn off the
NavigationButtons property but the more important question is why. If it's
because you need to run some code before a record is saved/changed, then you
really need to move that code into Form_BeforeUpdate. That's the only way
you can guarantee it runs regardless of how the save occurs (e.g. menu,
keyboard shortcut, menu, closing form, closing Acess, applying a filter,
changing sort order, clicking in a subform, and so on.)