All built-in ( or "system") properties assigned to a particular root class are inherited by all its subclasses. Similarly, all custom properties added to a class are inherited by all of its subclasses.
If you..
Add a custom property to a superclass --
The property is added to all new and existing subclasses; however, the property in the existing versions has no value.
Delete a custom property from a superclass --
The property is not deleted from any subclasses. After you delete the custom property from a superclass, you can manually delete it from its subclasses.
Update a custom property on superclass --
The change propagates to new versions and subclasses. The property is not updated in existing subclasses and versions.
Add an alias ID to a superclass --
The alias ID is added to all subclasses.
Change a property's value for Read Only, Value Required, or Settability --
Change the Maximum Length for a string or binary property --
The change propagates to subclasses with a higher maximum value or where the value was not set.
Change the Minimum Value or Maximum Value of a property --
The change propagates to all subclasses where the current value is less than the new value, or where a value is not set.