Development Discussion Board

Nope. You need to do that through an FTP client.

Pretty much all of those things should be done by extensions. What you "need" many others don't need or even want.

Report it in the Customisations DB tracker as the demo doesn't have anything to do with phpBB itself.

If there's a bug you've found that you think needs addressing then any review and/or work would be done off of the tracker, not from a forum post. If for some reason you're unable to do that then let us know.

This looks more like a bug report that needs to be reported to the tracker.

This forum is for development discussions about our main product. For anything else please search or ask on our main forum at https://www.phpbb.com/community

The new style will not be in 3.3 if that's what you're referring to.

Errors come up during cache building (like after a cache purge), but only then and they're more like warnings. You would not be able to install a new instance of phpBB while running PHP 7.3. I run a test board on 7.3 as well but there are certain things that don't work correctly although those thing...

3.3.0