You can configure the system to allow image upload only for registered users. For more image upload options check this link: https://chevereto.com/docs/image-upload
Regarding themes I'm afraid that there are no additional third-party themes available right now.
I'm confused here. Your posts looks like someone who is already running Chevereto but you clearly don't have the client badge. I don't feel confortable exchanging more information with you if you don't clarify things for me.
When I get into the Chevereto Admin panel there are not many options and only thing that I can deleted image. The other options I do not possess on admin panel.
Looks like I have a basic version. I Wonder where I can buy a script but only script v. 3 ?