Was the religion of Islam present before the Prophet's mission, and were there Muslims, and what is the ruling concerning those who died in the pre-Islamic era (Jahiliyyah) before his mission?

Islam is submission and obedience to Allah and worshipping Him alone, according to what He revealed to His prophets from Adam to Muhammad, peace be upon them all. All prophets and their followers were Muslims. If by Islam this general meaning is intended, then it existed before the Prophet Muhammad, peace be upon him, but only a few remained steadfast upon it at the time of his prophethood. However, if the specific meaning is intended, then the Prophet Muhammad, peace be upon him, was sent during a period of absence of messengers and cessation of revelation, after corruption and ignorance had become widespread, with the exception of remnants among the People of the Book. As for the fate of those who died before the prophethood of the Messenger, peace be upon him, the most probable view is that Allah will test them on the Day of Judgment with fire. Whoever plunges into it will enter Paradise, and whoever refuses will enter the Fire.