Is congregational prayer in the place of a demolished mosque, where the nearest mosque is a 10-minute walk away, considered prayer in a mosque, and will those who pray there receive the reward of congregational prayer?

Your prayer in the congregational mosque is better and carries more reward, according to the Prophet, peace and blessings be upon him: "A man's prayer with another man is purer than his prayer alone, and his prayer with two men is purer than his prayer with one man. And the more (people there are), the more beloved it is to Allah Almighty." Nevertheless, your congregational prayer in the old mosque's location will still earn you the virtue of congregational prayer.