This:

Variables.Data = {0400000001000000060000003A494400301A050000000000000000000000}

Is never written by Delphi 2006. This is only written by Delphi 2009 to support the new string format. You cannot edit the same forms in Delphi 2006 and Delphi 2009. Once you migrate to Delphi 2009, you cannot go back with modified forms.

Can i build delphi 2009 version source code under Delphi 2006?

Yes, that should work.