Is ghusl obligatory upon the recipient of sodomy, knowing his ignorance of the ruling? And is he required to repeat the prayers he performed without ghusl? And is puberty a condition for ghusl?

There is no distinction between the active and passive parties in the obligation of ghusl due to janabah. Ghusl is obligatory for both the one who engages in intercourse and the one upon whom it is performed, if they are eligible for ghusl. If the person upon whom it was done does not perform ghusl, their prayer is invalid due to the absence of the condition of purity, and they must make it up according to the majority of scholars, whereas Ibn Taymiyyah holds that one who omits a condition due to ignorance is not required to make it up.

Puberty is not a condition for the obligation of ghusl. A discerning child, if in a state of janabah, must perform ghusl for the validity of their prayer, as purity is a condition for the validity of prayer, whether one is an adult or not. However, a child is not required to make up missed prayers from before puberty. If a discerning child performs ghusl, their ghusl is valid and does not need to be repeated upon reaching puberty. The guardian must instruct the discerning child to perform ghusl. The obligation of ghusl for a minor means that it is a condition for the validity of prayer, circumambulation (tawaf), and reading the Qur'an, and not that sin is incurred for its omission.