Breakpoint is the term Elementor uses for when a responsive screen changes

Default property

The bigger device setting always takes precedence

For any element property that can have different response settings (Desktop/Tablet/Phone), the bigger device setting takes precedence.

So values given for desktop will apply for tablet and phone also unless they are given their own value.

For a property that has different responsive settings availalbe, the screen icon is shown next to its name. Elementor defaults to desktop (of course!).

Changing column to full width on smaller devices

Set its width to 100% fore that device screen size (biggest device takes precedence, so setting for tablet will also set for phone).

Altering column order when changed to on top of each other for mobile

Select the section > Advanced > Responsive > Reverse Columns

Screen Width Definitions

(Desktop / Tablet / Mobile / Your own custom definitions)

Site Settings > Layout > Breakpoints

Menu behaviour

Site Settings > Header and Footer