Muslims have memorized the Quran for a very long time. There are early versions of the Quran that are exactly like the quran from now. if it were to change Muslims woudl remember the old one and bring it back
PEOPLE AFTER THEIR RELIGION FORBIDS HUMAN RIGHTS (IT HAS DEFINITELY BEEN CHANGED MULTIPLE TIMES OVER THE YEARS AND ANYONE COULD’VE ADDED ANYTHING THEY WANTED):