Is the prayer valid in a mosque where the iqama is delayed for more than 25 minutes and the imam prolongs the prayer until dawn appears, knowing that it is the closest mosque to the home?

The Sunnah regarding the Fajr prayer is to perform it early (at "taghlees"), and this is the opinion of the majority of jurists, in contrast to the Hanafis who held the view that it is recommended to delay it until "isfar" (when light spreads), but without delaying it to the extent that one doubts the sunrise. The prayer is considered to be performed on time if it is before sunrise, and it must be performed at its legally prescribed time, as Allah the Almighty says: "Indeed, prayer has been decreed upon the believers a book [due at] fixed times."