For the purpose of determining the property rights of any person under any nontestamentary instrument, an adopted child’s relationship to his or her adopting and natural parents shall be governed by § 2-4 of the Probate Act of 1975. For the purpose of determining the property rights of any person under any nontestamentary instrument, the changes made by this amendatory Act of 1997 apply to all nontestamentary instruments executed on or after January 1, 1998.