yes, in "The Sight"
Graystripe returns in The Sight, in Chaper 10.
It was considered and many cats wanted it, but Brambleclaw remains deputy for now.
Yes, when Graystripe returned to the clans after being abducted by twolegs, Firestar was still the leader. However, Graystripe's position as deputy had been filled by Brambleclaw, who remained deputy even after Graystripe's return.
Graystripe meets Millie in the Warriors book series during the third series, Warriors: Dawn of the Clans, in the book titled "The Sight." Millie rescues Graystripe from Twolegplace and helps him find his way back to ThunderClan.
As of 'Sunrise', Graystripe is in Thunderclan. If you are asking about where he was when he was taken by the twolegs, he became a kittypet, ran away, and set off on a journey to get back to Thunderclan. You can read about this in the Warriors magna series.
Graystripe.
Graystripe comes back in the power of three book 1 The Sight
Graystripe is a gray tabby with a darker stripe running down his back, starting at the back of his head to his tail-tip. greystripe is a nebelung,not a tabby
Millie loves Graystripe because he has shown kindness, loyalty, and courage. They have gone through many challenges together, and their bond has grown stronger as a result. Millie admires Graystripe's resilience and determination, which have earned her love and respect.
Graypaw's mentor was Lionheart but then after Lionheart dies Graypaw becomes a warrior, so as far as I know he does not receive another mentor. He becomes the mentor of Brackenpaw when he is Graystripe.
In this book, Graystripe is still prisoner with the Twolegs.
Graystripe returns in The Sight with a new special someone. Her name is Millie. She was a kittypet until Graystripe trained her to become a true warrior. She later conceive his kits. Now known as Briarlight, Bumblestripe and Blossomfall.