Due to ignorance and the prevalence of non- religious conditions, over a period of ten years an individual had performed obligatory Ghusl without observing its sequence and later came to know that sequence in Ghusl is obligatory, what is the ruling for all their past Ghusl?

For the authenticity of Ghusl, the known sequence - first the right followed by the left side of the body - is not a condition, even if the dedication of the body in respect to the head and neck is incorrect. All cases in which it becomes known after a period of time has passed that the Ghusl performed are invalid, it is not obligatory to repeat all prayers and fasts.