Back up the specified folder once a day → Will it be backed up from one computer or multiple computers to the NAS? (We can do both.) Besides overwriting when there are updates, if files are removed from the PC, should the files also be deleted remotely, or should they be kept?

Actually, I want to copy all the data from my own computer to the NAS (probably just some specified folders), so that employees can access my latest progress at any time.
If there are updates, overwrite them. If files are deleted on the PC, it’s okay to sync the deletions as well. However, if it’s possible to keep deleted files for a period of time, that might be a good option (to avoid accidental deletions). Is that doable?
Can be used on the public network → Is it read-only, or can it be written as well? Does this refer to sharing via SMB (Network Neighborhood) on the network? Sharing with macOS and PC?

Yes! The concept is like Network Neighborhood, so that colleagues connected to the same network cable can all see the folders I want to share with them, and can also help supplement the completeness of this folder.
So, theoretically, this NAS is shared at a certain level, but I’m worried that colleagues might accidentally delete or wrongly edit my files. Is there any solution for this in the system?
Sharing with Windows PC
Can be used outside the company → Mobile phones can connect via App, and for PCs, we provide VPN or web interface access.

That’s great, so I can access it anytime.
Above all, you’ve summarized my needs very thoroughly!
Thank you very much.