I went through all Liquipedia pages covering tournaments from the 2000s to collect this data. Obviously, some of the information isn’t perfectly accurate — not every event had complete records. Still, the results turned out to be interesting.
➡ Montenegrin players effectively debuted in the same month Montenegro declared independence; however, new passports had not yet been issued, so they competed under the Yugoslav flag.
➡ Lebanon is the only country where the first professional debut was made by a woman rather than a man.