Was the Prophet Muhammad sent to all mankind?

Every Prophet or Messenger before the Beloved Prophet Muhammad ﷺ was sent to his own nation, but the Beloved Prophet Muhammad ﷺ was sent to mankind at large. This implies that every human being must follow the Last Prophet Muhammad ﷺ, because he is sent to the whole of mankind. As Allah mentions in the Qur'an:

"And We have not sent you but as mercy for all the worlds" [Qur'an, al-Anbiya 21:107]

Allah took a covenant from all of the Prophets that they must believe in Muhammad ﷺ and support him. As Allah mentions in the Qur'an:

"And when Allah took a covenant from the Prophets, saying, since I gave you the Book and the wisdom and then when a Messenger comes to you believing what is with you, you should believe in him and support him. Allah then said, 'Do you testify to this and accept this covenant?' They said, 'We agree and testify to it.' Then He said to them, 'Therefore, bear witness and I do so along with you.'" [Qur'an, Al Imran 3:81]

Every Messenger gave his people the glad tidings of the Last Prophet's ﷺ advent as a Messenger:

"And when Eesa, son of Maryam, said, 'O Children of Israel! Surely I am the Messenger of Allah to you, ascertaining that which is before me of the Torah, and giving glad tidings of a Messenger who will come after me, his name will be Ahmed.'" [Qur'an, as-Saff 61:6]

Hence, whoever believed in Musa peace be upon him, Moses, until the advent of Eesa peace be upon him, Jesus, it was mandatory on him to believe in Eesa peace be upon him and follow him. Since Muhammad ﷺ is the last of the Messengers that Allah sent to mankind, it is binding on every human being to believe in him, adhere to his guidance, and love him.