A:  The CURRENT uncertainty in parallax measurements
            by Gaia is, very roughly, about 0.2 mas.

      If we adopt the very rough rule that one should
            only use parallax values which are at least
            10 times larger than their uncertainties,

               maximum "good" parallax  ~  10 * 0.2 mas

                                        ~   2 mas


               maximum "good" distance  ~  500 pc