The files inside the folder is shareable to other people. Also, I can open the file in the incognito window. Likewise, can I share the folder or make the folder public?
Short answer: Currently, no.
From the APIs and references, it doesn’t seem to be possible to convert the folders to be public; you can however make all the files public within a folder, you can read more on that here.
Maybe some day an update will be made available online to support folder access levels too, but currently it is all about files. You can read the CLI reference here to explore how you can recursively convert the files to be public.