Is it obligatory to make up prayers missed since puberty and during a period of irregular prayer, and what should I do if I cannot determine their number?

One must perform ghusl immediately upon seeing the sign of purity, based on the statement of Ibn Abbas (may Allah be pleased with them both): "It is not permissible for her, when she sees the sign of purity, even for an hour, except that she performs ghusl." Therefore, the prayers missed during this period must be made up. If the number of prayers is unknown, then one should make up what is most likely to clear one's conscience. As for the two years during which prayers were abandoned, it is more cautious to make up all those prayers as much as one is able, without harming one's body or livelihood.