What is the ruling on vocalizing the remembrances (dhikr) after prayer, and on following the imam in their recitation and number, and what is the ruling on consistently performing the Qunut supplication after the Fajr prayer?

The default is for the Imam and congregants not to vocalize the adhkar (remembrances) collectively after prayer, except for the purpose of teaching. If the Imam knows that the congregants need to learn them, he may vocalize them until they learn, then he should recite them silently, while gently explaining the ruling to them. The Qunut in the Fajr prayer is prescribed by many scholars. The prostration of some congregants, due to their assumption that the Qunut was forgotten, does not invalidate their prayer. The wording of the adhan (call to prayer) is fixed and divinely ordained; adding to it with prayers upon the Prophet (peace be upon him) or anything else is not prescribed.