What is the ruling on someone from whom semen was discharged, so he washed his private parts, performed ablution (Wudu'), and prayed due to his ignorance of the obligation of ghusl (ritual bath), and this act was repeated for 5 years? Does he have to repeat the missed prayers?

If someone emitted semen and only washed their private parts out of ignorance, then performed ablution (Wudu') and prayed, they have, out of ignorance, omitted a condition for prayer. Scholars have differed regarding the obligation to re-perform the missed prayers. Some have gone to the extent of saying there is no re-performance, while others have gone to the extent of saying it is obligatory to re-perform them, and this is the view given in fatwas. Based on the view that re-performing is obligatory, the person must re-perform all prayers that passed without ghusl (full ritual bath). If they cannot ascertain the number, they should continue re-performing until they are reasonably certain they have absolved themselves.