If one makes up missed prayers with the intention of precaution, will what exceeds the missed prayers be counted as supererogatory and be rewarded for it?

Whoever missed prayers and does not know their number or how to make them up, if he absolves himself with certainty, then he is a doer of good and will be rewarded for his action. Indeed, his prayer will not go to waste, even if it was not obligatory, because Allah does not let the reward of those who do good go to waste. And that would be a voluntary act for which he will be rewarded by Allah.