If the project owner has paid for pro, all collaborators can use the pro features in the project.
Zotero sync is just a .bib file that updates itself regularly, so if you don't want to pay, you have to upload the .bib file or past the new entries manually.
yes, cross-references are possible by adding an <anchor> and referencing it with @anchor. It works for headings, figures, equations, footnotes, and with a slightly different syntax also for page. [1]
Numbered lists are currently not natively supported, only with the package itemize [2].
I noticed quite a few people must do that because I have heard that pronunciation a few times already IRL and in videos. Some people also write it that way, a search here in the comments results in 4 matches.
There is currently work done to support basic HTML support. PDF is supported since day one of the public release in march 2023 (before v0.1). The roadmap mentions tagged PDF which is mainly needed for accessibility.
Zotero sync is just a .bib file that updates itself regularly, so if you don't want to pay, you have to upload the .bib file or past the new entries manually.