You should be able to do all that in a github codespace which is free to use for personal accounts for some time and data limits. But at that point I would probably install a VSCode or similar locally instead.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
No, I'm pretty sure you can't - and it doesn't look like there's anything built in for renaming folders (at least at first glance)