Except with the approval of the commissioner and under such conditions as to investments and other matters as he or she may prescribe, which shall recognize the guaranteed nature of the benefits provided, reserves for (a) benefits guaranteed as to dollar amount and duration and (b) funds guaranteed as to principal amount or stated rate of interest shall not be maintained in a variable product account. The reserve liability for variable products shall be established by the insurance commissioner pursuant to the requirements of RSA 410, the standard valuation law, in accordance with actuarial procedures that recognize the variable nature of the benefits provided.