Does the discharge of a single drop of blood at the age of 12 indicate puberty, and is it necessary to make up for the Ramadan fast that followed?

The majority of scholars hold that a drop of blood is not considered menses (hayd), because it is less than their minimum duration for menses. Whenever blood is less than its minimum, it is considered istihadah (irregular bleeding). The minimum duration for menses according to the Hanbalis is one day and one night. Therefore, this drop of blood is not considered menses unless the bleeding continues for a full day and night. Consequently, you did not reach puberty with it, and thus the fasting of Ramadan that occurred before puberty was not obligatory upon you.