Charles-Valentin Alkan's '12 Études pour les pieds seulement' are actually part of his 'Trois grandes études' (Op. 76), specifically the third study, which is written for organ pedals. The description of it being for piano is factually incorrect as it is an organ work.
The primary challenge is the extreme physical coordination required for pedal-only performance on an organ.
12 Études pour les pieds seulement is rated Henle level 8 of 9 — concert repertoire, roughly diploma level.
You should be comfortable at Henle level 8 — meaning you can already play level 7–8 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
12 Études pour les pieds seulement is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.