org-tags-view shows matches in all agenda files: you have to add this file to your agenda files (at least temporarily). You can do that with C-c[: that adds it to the front of the agenda files. You can later delete it from the list if you want with C-c] (this will delete the file at the front of the list, so I'm assuming you have not added any other files in ...
I don't think it's already in Org.
(defun my-org-sort-tags ()
"On a heading sort the tags."
(org-set-tags (sort (org-get-tags) #'string<))))
for a start?
You can also pass the results to R (or some other program) to do the
(dolist (tag (org-get-tags))
(push (list tag) tags))))
#+begin_src R :var tags=tags
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