How can I restrict users from creating New Topic? Only Admins and Moderators should be able to do that.
ACP > Manage > Privileges, then select each category from the dropdown at the top right and set the privileges accordingly.
I am heavily dependent on HTML for customizing posts, so how to restrict general users from using Markdown HTML. Can we use two different Reply solutions for users and Mods? I mean only Admin and Mods should use HTML in the posts.
Not yet, but there's an issue for this on the markdown plugin repo.
Is there any way to restrict quoting Admins or specific post?
I don't think so, but you can disable mentions notifications if you're having annoying notifications all the time.
Is there any way to start on shared hosting. I know till 2016 it was, NO, but anything changed after that?
The way Node.js (which is the platform that NodeBB runs on) works isn't really compatible with shared hosting.