People assume a money-back guarantee needs unopened product. The page does not spell out either way.
We do not know whether the guarantee covers opened or finished bottles, whether bottles must be returned or who pays return shipping. The page tells you to confirm current terms on the official checkout.
On a short pack the product may run out near the end of the 60 days.
Read the refund policy before you start, and ask the seller in writing whether finished bottles qualify. Do not wait until the product is gone to ask. Keep your order email and write down your refund deadline. Our guide to calendaring the deadline shows how.