Is praying Asr individually, whether in the mosque or at home, rewarded the same, knowing that there are no other worshippers in the mosque for Asr prayer?

If you are certain that you will not find anyone to pray Asr with you in the mosque, but you can gather a congregation outside of it, then it is better to pray in a congregation, based on the saying of the Prophet (PBUH): "A man's prayer with another man is purer than his prayer alone, and a man's prayer with two men is purer than his prayer with one man, and the more numerous they are, the more beloved it is to Allah, the Almighty, the Majestic."

However, if you cannot find a congregation neither inside nor outside the mosque, then it is better to pray in the mosque due to the encouragement to maintain it, as stated in the verse: "The mosques of Allah are only to be maintained by those who believe in Allah and the Last Day and establish prayer and give zakat (definition) and do not fear except Allah. For it is expected that those will be among the guided," and the saying of the Prophet (PBUH): "Whoever goes to the mosque in the morning or in the evening, Allah prepares for him a lodging in Paradise every time he goes in the morning or in the evening," and "Whoever purifies himself in his house and then walks to one of the houses of Allah to fulfill an obligation from the obligations of Allah, one of his steps erases a sin and the other raises a degree."