Hi, welcome to the community.
Nope. You can use whichever code editor you want, providing that it can deal with multiple languages - as the Full Stack course will involve several.
I’ve never used PyCharm personally, so I don’t know much about it. I’m fairly sure it’s geared for working with Python, though, so may not be a great choice for the Full Stack path? You’d be better with a more general code editor / IDE.
Ah, not a fan of Microsoft? Quite a common opinion, though from experience I find a lot of the time it’s people bashing them for historical reasons…
You don’t have to use VS Code, as I’ve already mentioned, but it’s a good code editor.
Also, Microsoft are pretty sizeable contributors to open-source… alongside their seat on the board of the Linux Foundation, as @stetim94 mentioned, they’re involved with a lot of other technologies that you’re likely running… Node.js for example.