Maybe looking at the music yourself and forming your own assessment is better than an abstract estimate about grade levels. If it's any help: I've played this for years (never very well) and disagree with people who see it as the easiest Chop etude. I for one find the black key etude and even the 3rd ballade easier. I find it really hard to get the phrasing in 25/1 to make any sense. And a few times there's a sort of countermotif just off the beat to be played by the right hand 2nd finger, which require a pretty big technique (if you want it to sing properly). This is done well by Horowitz (last cd), Sgouros and Cziffra, but I've heard some other pianists not playing the countermelodies.
I do find 25/1 a good warmup piece since it gives most fingers a workout. It's horrible to misuse beautiful music like this, but then Arrau used to play the Hammerklavier fugue 6 times daily to train stamina.