Is a mosque that was originally an apartment and was not built as a mosque from the beginning, but later became a mosque, considered a complete mosque, and is the reward for congregational prayer therein diminished?

If a house or shop owner decides to convert it into a mosque, or if some people wish to purchase it and convert it into a mosque, there is no harm in that, and it will then be subject to the rulings of mosques. Muslims have often converted many places of polytheism into mosques, just as the Prophet, peace and blessings be upon him, ordered the construction of a mosque in Ta'if where their idols once stood. Places of disbelief and disobedience were transformed into places of faith. If there are no longer any Dhimmis who deserve their places of worship, it is permissible to convert them into a mosque. As for building a mosque or converting a building into a mosque in an area expected to be devoid of Muslims, it is permissible due to the public benefit and the manifestation of the rituals of Islam. If a mosque becomes too small for Muslims, or if the town becomes empty of them, it is permissible to sell it and use the proceeds to build another mosque.