How do I call vectorp and aref twice in a cond statement

;I got this whittled down as much as I can...for some reason I cant call (aref arg i) in a cond statement twice in a row. I do have to verify it is a vector 2 different ways, before I run (aref arg 0) and (aref arg i) as below...How can I do this?...I'm getting deleting unreachable code error.

(defun vector-test (&optional arg i)
  (cond ((vectorp arg)  (aref arg 0))
        ((and (vectorp arg) i)  (aref arg i))))

If the second condition is true, the first condition also is true, so the first will be executed.
you could change the lines or use multiple ifs like this:

(defun vector-test (&optional arg i)
  (if (vectorp arg)
    (if i
      (aref arg 0)
      (aref arg i))))