Are the remembrances mentioned in the two hadiths restricted to a specific time (morning and evening), or are they permissible at any time, and does the reward differ between the hadiths (four slaves and ten slaves)?

The dhikr mentioned in the question has come down through various narrations, resulting in differences regarding its timing. This indicates the permissibility of reciting it multiple times a day at different times. If this tahlil (لا إله إلا الله - There is no god but Allah) is recited more than one hundred times a day, the reciter attains the reward mentioned for the hundred, and receives further reward for the increase. This is not considered among the prohibited excesses; rather, an increase in good deeds is مطلوب (desirable/sought after). The apparent generality of the hadith indicates that the reward is attained by reciting the tahlil one hundred times a day, whether consecutively or separately. It is preferable to recite it consecutively at the beginning of the day so that it may serve as a protection for the reciter throughout their day.