FM gets its stats from a highly reputable professional football player scouting company, a company used by many many clubs. What it cant do, however, is predict the future. I'm pretty sure in FM 2002 there were wonderkids who today are unknown.
Yes, but not only.
A lot of players in FM who are not from major leagues are not scouted by anybody else, but the fans of the game, who agree to be researchers.