Is the saying correct that the Victorious Group (الطائفة المنصورة) was not present at the beginning of Islam and will appear at the end of time, its location being the Levant (الشام), and that it will remain until it fights the Antichrist (al-Masih ad-Dajjal)?

The origin of the Victorious Group (Al-Ta'ifah Al-Mansurah) are the Companions of the Messenger of Allah, peace and blessings be upon him, then their successors, and the successors of their successors, and everyone who follows their methodology. They are the Saved Sect (Al-Firqah Al-Najiyah) who are upon what the Prophet, peace and blessings be upon him, and his Companions were upon. The implication of the hadith (definition) "There will always remain a group from my Ummah" indicates that this group has existed and will continue to exist until the command of Allah comes. Their presence in Ash-Sham does not negate their presence in other places, nor is it necessary for them to be gathered together.