100 editions of the Tour de France, 1912

1912 Alcyon ridden by Odile Defraye BEL

1912 followed the formula of the 1911 Tour, which many saw as the first 'modern' Tour, setting the tone for all future editions, though with stages like the marathon 470k and 16 hour haul from La Rochelle to Brest it still owed much to those earlier events. 15 stages and 14 rest days is not something we see today, though at least they lifted the ban of freewheels (some of the facts around this are lost in history because earlier editions allowed freewheels but at some point they were outlawed. Desgrange tinkered with the rules in the same way they do in F1 today).
Jean Alavoine took advantage of the rules change and in fact rode with an early gear changing device which helped him to win three stages.

10 teams of 5 lined up at the start with the rest of the 131 man field being independent riders. Petit-Breton was riding for Peugeot, who were back after their self imposed boycot of the race, though he was again unlucky, this time quitting after crashing into a cow.

Eugène Chrstophe finished second overall, though he could've won if not for the points system that favoured more conservative riders, and on the way took a stage after possibly the longest breakaway in Tour history. Attacking in the Alps and taking in the Télégraphe and Galibier he stayed away for 315k and finished 30 minutes ahead of Defraye.

Riders on the Aubisque during a rain soaked 326k and 14 hour stage

In the end Defraye won easily when the other Belgian riders helped him even though they were on other teams. The French La Française team was so upset by this blatant rule breaking they quit the the race.