A person performed actions without following any specific tradition for a period of time, then later realized…

Answer

In the name of Allah, know, my dear, that there is no normal person who has completed their prayer and does not know how they prayed. However, it is possible that other actions, whether a long or short time ago, may have been forgotten in terms of how they were performed. In any case, they should follow the guidance of someone qualified for following (taqlid) among the Shi'a, and the most knowledgeable among them. They should compare the prayer they just completed with the rulings of the scholar they follow. Similarly, they should review their previous prayers in the same way, based on how they prayed last. They should compare their actions with the fatwas of the scholar whose rulings they have adopted. If their actions require repetition (re-doing), they must repeat them according to the fatwa of the scholar they follow. Allah is the Guide and All-Knowing.