Nobody knows git. We all just run the few basic commands, then again with the -f switch just in case. Then if that doesn’t work, reclone.

As a hiring manager, I’m always interested in seeing a candidate’s exercise of their skills. But “from absolute scratch” is not something we really do in the working world if we can possibly avoid it, so I wouldn’t expect it in your portfolio. If you’ve got some amazing JS or CSS to show off, definitely do so, but point it out because I’m otherwise expecting frameworks.

Ethically there are no problems with libraries and frameworks. If you’re using them consistently with the creators’ licenses, we’ll, that’s what those things exist for.