The entire piece is an etude if you want to look at it that way. Just make sure the action is well-regulated because not all pianos allow the piece to be played.
TOO true.
Look.. this piece is an absolute beast. Not recommended for people with an intermediate level of technique. There is really no piece that I can think of that will prepare you for HR2.
Some things you need to be able to do. 5-3 trills, crazy prolonged tremolos that exceed an octave, SUPER fast scale work, poly-rhythms in the Lassan section, stamina, strength, you'll need to have good keyboard geography (things happen so fast that you can barely see what you're doing half the time)..
To be honest, people often claim that they can play this piece, when in fact, there are very few people who can actually play it well. The physical and technical demands are endless.
Don't rush to play this piece. It's a killer. I played it briefly about 10 years ago, but I don't play it anymore.. it's too much work.
Is it the hardest piece ever written? No, but nevertheless it's CRAZY hard. One of the hardest pieces I've ever played for sure.

If you're aching to play a Rhapsody, I'd think about tackling 11 or 13 or the 3 late Rhapsodies. They are more accessible (and still insanely hard).
Good luck to you!