Most of the Chopin Etudes including 25/9 are beyond what is required for ABRSM 8, based on their repertoire lists. To play it at tempo requires an advanced technique. I would say 25/2 is beyond ABRSM 8 as well. But I would encourage any piano student to study the Chopin Etudes. Also Czerny Etudes. Isn't your piano teacher guiding your selection of pieces?