Does repeatedly performing the obligatory prayer bring the reward of the obligatory act each time, and is it more meritorious than performing supererogatory prayers, and is it permissible to perform obligatory duties such as fasting and zakat multiple times in a single year to obtain the reward of the obligatory act each time?

Repeating an obligatory prayer without a valid reason is disliked (makrooh), as mentioned by Ibn Taymiyyah. If a Muslim has prayed and then a congregation gathers, it is recommended for him to pray with them, and this prayer will be considered a supererogatory (nafilah) act. Whoever repeats an obligatory prayer several times without a legitimate reason has committed something disliked. He should instead pray as many supererogatory prayers as he wishes, rather than repeating the obligatory one.

As for zakat, whoever has paid what was due from him has fulfilled the obligation, and whatever he gives thereafter to the poor is a voluntary act, for which he is rewarded with the reward of a supererogatory act, not an obligatory one.

Similarly with fasting, whoever has fasted Ramadan has fulfilled the obligation, and whatever he fasts thereafter is a voluntary act, for which he is rewarded with the reward of a supererogatory act.

The obligatory acts are the greatest means by which one draws closer to Allah, and their reward cannot be compared to the reward of supererogatory acts; this is due to the saying of Allah in the Hadith Qudsi: "My servant does not draw near to Me with anything more beloved to Me than what I have made obligatory upon him." The reward of an obligatory act surpasses the reward of a supererogatory act.