1)
Why does the Torah insert this (otherwise superfluous) Pasuk?
1.
Rashi: To teach us that the three Arei Miklat that Moshe set aside in Eiver ha'Yarden 1 will not take effect until Yehoshua designates the other three in Eretz Yisrael.
1
See Torah Temmah, note 18. See also the following Pasuk.
2)
What are the implicatons of the word "Sheish Arei Miklat Tih?yenah lachem??