If a Muslim prays in congregation at the Prophet's Mosque, the Sacred Mosque, or Al-Aqsa Mosque, will it be counted for him as 25,000 prayers or 27,000 prayers, and have any scholars stated this?

What the apparent meanings of the texts entail is that the multiplication of reward for congregational prayer over individual prayer applies to prayer in the three mosques, as there seems to be no issue in applying both multiplication factors simultaneously. This issue is a matter of consideration and research among some scholars, and no definitive statement has been found from any of them asserting or denying the simultaneous occurrence of both multiplications. Al-Hafiz Ibn Hajar narrated from Abu Bakr Al-Naqqash that the multiplication of reward in the Sacred Mosque exceeds a long lifetime, and that is regardless of the multiplication for congregational prayer. The question of whether both multiplications can combine is still under discussion.