Is it true that you ALWAYS need to work in your free time to be proficient at what you're doing (up to date with the newest technologies)? I do enjoy programming, I do like to work on my personal project from time to time but if you need to code all day long from morning to evening, yeah no thanks... I have other hobbies in my life.
No, not always, but I'd argue that at least a small commitment outside of work hours is required.
Any career prospects in the long term?
Yes, just maybe not in CRUD apps.
Hopefully this one makes sense : I do enjoy having this feeling of becoming good at something, like when you become a better cook by knowing how to cook multiple dishes. I just have this feeling that web development is about using tools that change every 2 months, so it means you can be a good web developper today but total garbage 2 months later if you haven't followed the trend. Is it actually true?
Learn the fundamentals and you'll notice most new frameworks are the same thing, slightly re-skinned.
Become good at learning new things, not good at one specific things and you'll be fine.