The shiny objects will begin having an use in the next patch.
The thorns will be posible to remove in the next patch too!
As for the holes, some are decorations but on the next patch some will have an use.
As for the bosses, not sure what you mean but you almost cleared it up. When entering the caves did you go to the right side at the very start?
If you cleared the right side at the very start you may be experiencing a bug, so let me know.
The next patch will have indicators on what parts are accesible and what arent.