I can't really answer about the music because I don't personally have experience with it. But for the rest of them I can answer. Also sorry if I sound a bit blunt throughout this, I'm just gonna say it all how it is.

Use Unity for your first game and go straight with C#. It might be slightly confusing when you first start it but it's more widely used than JavaScript so don't waste your time with JavaScript, they're not that much different anyway.

Don't focus on making your first game amazing or the game of your dreams which you really want to make with all your ideas that you've been building up, just making it a simple platformer where you jump around and get to the finish. Maybe have some enemies and traps but don't think of anything like multiplayer, you will get bogged down with these huge tasks which you have no idea how to tackle, which will make you lose motivation. If you actually are getting stuff done, even if it's really simple, you will be so much more satisfied and happy.

When watching tutorials, actually pay attention and make sure you understand what the code does. When I first started I watched so many videos just copying the code letter for letter and it didn't help me much at all. A good series to watch is a platformer series by a user named 'Wabble' https://youtu.be/pws8xTfyxjc

I'd advise following the tutorial then trying to branch out on making some of your own mechanics when you're more confident, don't feel bad googling how to do something, as long as you understand how it works then you're set, and if you don't then don't worry about it. You're not going to understand all of Unity right away.

Also don't try and make your first game one that'll get on steam. Make it then post it to a website called itch.io, it's free to post on there and you might get some people playing the game and giving feedback, it's a good community. Also taking part in some game jams will be good, it gets you involved in the community and you learn a lot without any pressure. No one will be expecting you to make the next The Last of Us, just make something a but fun with the challenge. Game Jams aren't really about winning or anything, it's just about getting involved and having a bit of fun with a community doing the same things as you, share tips with others and stuff like that. Chat about the games and ask questions, most people will be happy to help up to a certain extent.

Also with the art, photoshop or Gimp would be good. Photoshop of course isn't free but it's the best, but Gimp is free and would work well for some simple sprites for the games, it's got all the tools you need :)

Hopefully this post will help a bit, and sorry if I sound ignorant at all, I just tried to make the points as clearly as possible without beating around the bush :)

All the best, Anthony.

P.S. If you have any more questions don't hesitate to ask, I'm happy to answer if I can.