Can macOS show the Dock on all screens?
No. Apple's Dock shows on one display at a time and moves when you push the pointer to the bottom of another screen. There is no setting to show it everywhere.
The menu bar reached every screen in OS X Mavericks. The Dock did not.
If the Dock is missing on a monitor, push the pointer past that screen's bottom edge, or check that auto-hide and full-screen apps are not hiding it.