Back in the 50s and 60s, all FIDE titles were contested in best of 24 matches
Are you thinking of the World Championship, perhaps?
Because Beth Harmon didn't play in the World Championship. She played in open tournaments and invitationals.
Indeed, and at the end of the book, after beating Borgov she's looking ahead to the qualifying cycle to face Borgov in a World Championship match.
Many of the non-chessplayers who watched the series seem to be under the impression that she won the World Championship, but the series never said that, either.
The novel had a mix of fictional and real life characters. But the FIDE competition cycle did not sync with reality.
It's been a while since I read the book and I don't have it to refer to -- could you explain what you mean here? Based on the tournaments Beth played (if the dates in the show mirrored the book -- not sure about that either, or if years were given in the book), she wouldn't have entered the world championship cycle yet -- the 1966 US Championship would have been the zonal, but she didn't play in it, and the 1969 US Championship, the next zonal, hadn't happened yet.
Everyone starts as a beginner, from the least-talented patzer to the world champion.
GM Yasser Seirawan started at the age of 12 and in one of his first tournaments accepted that he lost in a non-losing position! By the age of 19 he was a GM. This video is funny when he shows how poorly he started his career, but has some excellent points for beginners (and possibly low intermediate players?). Audio gets better a few minutes in, but the first part is hilarious as he explains how he "lost" a non-checkmated game/position.