18-Month Extension of Transition Period and Delay of Applicability Dates; Best Interest Contract Exemption (PTE 2016-01); Class Exemption for Principal Transactions in Certain Assets Between Investment Advice Fiduciaries and Employee Benefit Plans and IRAs (PTE 2016-02); Prohibited Transaction Exemption 84-24 for Certain Transactions Involving Insurance Agents and Brokers, Pension Consultants, Insurance Companies, and Investment Company Principal Underwriters (PTE 84-24); Correction