The provisions of the constitution or law of any state expressly limiting the rate or amount of interest, discount points, finance charges, or other charges which may be charged, taken, received, or reserved shall not apply to any Federally-related loan:

Made after March 31, 1980; and

Secured by a first lien on:

Residential real property;

Stock in a residential cooperative housing corporation when the loan is used to finance the acquisition of such stock; or

A residential manufactured home: Provided, That the loan so secured contains the consumer safeguards required by § 190.4 of this part;

The provisions of paragraph (a) of this section shall apply to loans made in any state on or before the date (after April 1, 1980 and prior to April l, 1983) on which the state adopts a law or certifies that the voters of such state have voted in favor of any law, constitutional or otherwise, which states explicitly and by its terms that such state does not want the provisions of paragraph (a) of this section to apply with respect to loans made in such state, except that—

The provisions of paragraph (a) of this section shall apply to any loan which is made after such date pursuant to a commitment therefore which was entered into during the period beginning on April 1, 1980, and ending on the date the state takes such action;

The provisions of paragraph (a) of this section shall apply to any rollover of a loan which loan was made, or committed to be made, during the period beginning on April 1, 1980, and ending on the date the state takes such action, if the mortgage document or loan note provided that the interest rate to the original borrower could be changed through the use of such a rollover; and

At any time after the date of adoption of these regulations, any state may adopt a provision of law placing limitations on discount points or such other charges on any loan described in this part.

Nothing in this section preempts limitations in state laws on prepayment charges, attorneys' fees, late charges or other provisions designed to protect borrowers.