[Redstason]

Итак первое:

Код:

type
  TMyClass = class
  private
    { Private declarations }
  public
    procedure MyMetod(str:string);overload;
    procedure MyMetod(str:string;i:integer);overload;
    procedure MyMetod(str:string;i:integer;j:boolean);overload;

    { Public declarations }
  end;

Третье:

Код:

 type
  TAbClass = class
  private
    { Private declarations }
  public
   procedure MyMetod(str:string);virtual; abstract;
    { Public declarations }
  end;

 type
  TAb1Class = class(TAbClass)
  private
    { Private declarations }
  public
   procedure MyMetod(str:string);virtual;
    { Public declarations }
  end;