I don't know of any way to lock scroll bars in FileMaker.
What do you mean by "lock the menu at the top of the screen"? If you mean the grey horizontal bar called the status area, you can use a script with this step: Show/Hide Status Area [ Lock ; Hide ]
You can use File Options to set this script to run when the file opens. You can use the same script step in a different script with the "Show" parameter to unlock it when you as a developer need access to this area.