What episode does RIN appear in Naruto?
Rin makes a cameo before her actual introduction in chapter 122 and Naruto episode 72 during a flashback of the Third Hokage, and on the cover of chapter 16.
Was Rin’s death an accident?
It was an accident in which he honestly tried to avoid. At the time he was able to control Chidori. As he charged at a hidden mist Shinobi, Rin jumped in front of his Chidori, killing Rin.