When OldCreateOrder is false (the default) the OnCreate event occurs after all constructors are finished and the OnDestroy event occurs before any destructors are called. 

This differs from earlier versions of the library (distributed with Delphi version 3 and previous and C++Builder 1), where the OnCreate event occurred when the TCustomForm constructor executed and the OnDestroy event occurred when the TCustomForm destructor executed. Applications that require the OnCreate event and OnDestroy events to occur from the constructor and destructor of the form can set OldCreateOrder to true. 

OnCreate 

OnDestroy 

BeforeDestruction 

AfterConstruction