Delphi Parent class and subclass coercion type conversion problem

The expression of good words

1. Abstract method of abstracting the parent class is implemented by the quilt class, but the subclass implements its own method, and after the subclass (pointer) is cast to the parent class (pointer), the use of these different types of methods

The methods defined in the parent class can work as expected

However, the subclass's own defined method (not specified in the parent class) seems to be unable to be called by the converted pointer.

2. Various object-oriented mechanisms

Relationship of methods between parent and subclass: Overwrite, override, abstract ...

Delphi Parent class and subclass coercion type conversion problem