Is there a reward for praying alone in an abandoned mosque, and does Allah forgive sins through it?

Congregational prayer in the mosque is obligatory for every able-bodied person who hears the call (adhan). A Muslim should be diligent in attending it, especially in Western societies, so that it remains an Islamic environment for Muslims. Maintaining the mosque is a great act of devotion. Allah the Almighty said: (The mosques of Allah are only to be maintained by those who believe in Allah and the Last Day and establish prayer and give zakah and do not fear except Allah. For it is expected that those will be among the [rightly] guided). [9:18] Preserving the mosque as a vibrant place and advising Muslims to pray in it is important. Whoever calls to prayer and strives to establish it, but is prevented from congregational prayer by an excuse, it is hoped that he will attain its reward, based on the saying of the Prophet, peace and blessings be upon him: "Indeed, there are people in Medina who, whenever you travel a distance or cross a valley, they are with you." They said: "O Messenger of Allah, even though they are in Medina?" He said: "Even though they are in Medina; they were held back by an excuse." So, whoever intends good and acts within their capability will receive the reward of one who acted.