Always thought that the prophet Muhammed(PBUH) was the only messenger for all mankind as that what i usually heard from Muslim apologists and as in this Hadith
Abu Hurairah (may Allah be pleased with him) narrated that the Messenger of Allah (Peace be upon him) said, “I have been favored (by Allah) over all other Prophets with six (gifts which are): (i) I have been granted (the gift of uttering) the shortest expressions that bear the widest meanings, (ii) Allah made me victorious by means of awe, (by His frightening my enemies), (iii) the spoils of war were made lawful for me (iv) the earth was made for me (and my followers) a place for praying and a (means of) purification (i.e. one can pray in case there is no water through performing Tayammum (Dry Ablution, i.e. wiping one's hands with pure dust) (v) and I am the last of the Prophets.” He (peace be upon him) also said, “Every Prophet was sent to his nation only but I have been sent to all mankind.”
but then I heard that Noah (PBUH) and Adam (PBUH) were sent for the entire mankind of that time too, for example Noah (PBUH) prayed that all disbelievers to be destroyed and his prayer got answered and only people of his nations left, also for Adam (PBUH) it was only his nation so he was like a prophet for all mankind, so what is the difference between Muhammed (PBUH) being sent for all mankind and Noah (PBUH) and Adam (PBUH) being sent for all mankind.