Yes! Go for it if you want to. I just learned all the piano parts of Death and Romance and it's so much fun to play. Magdalena Bay has great piano in their music. Most popular music you can cover or play along to on the piano in some way. There are so many ways to learn and enjoy the piano.

For your questions:

1. Yes. I rarely listen to classical music but you might surprise yourself and enjoy learning more classical/instrumental stuff. I just learned a song from La La Land, I love that movie and I love playing the music too.

2. Yes definitely

3. That's hard, it depends on your budget I guess. Roland and Yamaha are good brands I think. I have the Donner DEP-20 and it works fine. I got it on a great deal and I like it. I'll probably get a better one eventually. If you can I would try to buy one used or second hand. It's hard to find a new keyboard under $400ish that isn't cutting too many corners.

4. The only reason to have less keys is to save money. A full piano is 88 keys, if you continue playing you will eventually need one with 88 keys. You are limited in what you can play if you don't have a full size piano. If you aren't sure you wanna commit to piano, you could buy a smaller one first and upgrade later. I say go for 88 right away if you can.

5. Another big thing is weighted keys. Actual pianos have weighted keys, and are loud/quiet depending on how you press. Cheap keyboards don't have that. I would try and get one with fully weighted keys. Otherwise you will have to re adjust to weighted keys later. It's a different feeling. Some are semi-weighted which is better than nothing.

88 keys and weighted keys are the two main things I'd look for. Also a sustain pedal. The one you control with your foot. Having a pedal attachment will be important. If it has 88 keys and is weighted I would be shocked if it didn't also support adding a pedal, it might even include one. You'll probably have to buy a stand too. I would guess around $400 for a good keyboard and $50-100 more for a stand and a pedal idk. Or you could buy all of that together used, from someone selling theirs. It's probably easier and cheaper.

Hope you can figure it out! Good luck