A few things to note:

First: Kakashi's age. There seem to be some inconsistencies in the databooks and manga with all the recent flashbacks, but I always considered that big group shot of everyone at the Entrance Ceremony to be those who were entering the Academy for the first day of classes in general, whether it was their first year being there or their fourth. Plus, it was a rare opportunity for Kishimoto to show ALL the prominent characters from that generation as kids in one shot. Heck, I basked in that fanservice like a giddy pre-teen cause they're all so CUUUUUUUUTE! XD

So, in an effort to make things "logical", I took the ages of graduation as my base for a timeline. According to Narutopedia Kakashi graduated at 5, and became Chuunin at 6. Obito and Rin graduated at 9, which makes them 3 or 4 years older than Kakashi since they were all in the Chuunin exam together. Obito was 13 in Kakashi Gaiden, which makes Kakashi 9 or 10 when he becomes a Jounin and gets the sharingan. I went with the idea that Kakashi was 10, and Obito was nearly 14.

Following that line, the Third War grinds to an eventual halt and there's no way to tell how long Obito was unconscious while Madara kept him prisoner. His montage of healing and getting stronger was paced to suggest several months to a year, so all together it might have been nearly a year and a half. This means that Kakashi was probably 11 (nearing 12) when Rin died, and she and Obito would have been around 15. Minato becomes Hokage soon after that since he had been "out on a mission" when Rin was kidnapped/killed, implying he wasn't Hokage at that time.

Second: I have not yet watched the "Kakashi: Shadow of ANBU" anime arc, I've only read a few spoilers. This story was already half formulated before I read those spoilers, so all I really did was tweak it a bit and add a few things to sort of follow what little I've read. It's not entirely accurate because this story is first and foremost a part of the universe I've already created, but I did try to write it in a way that you can enjoy this piece without needing to read anything else I've written.

However, for anyone who wants to know: The date of Sakumo's death is from my story "Out Flew the Web and Floated Wide". My headcanon regarding ANBU code names is from the first part of Chapter 9: Onigawara in "Certain Things Rearrange...". ( don't worry, it's very short, and you honestly don't have to read any farther than the obvious exposition at the beginning. The rest of the chapter is an alternate POV on another story, so feel free to ignore it if you haven't read "Things Just Ain't The Same...". ) Kakashi's first glimpse of Naruto is a reference from "Don't Cry". How he received his first copy of Icha Icha, as well as his circumstances for being a Jounin Sensei candidate, are from "Notes". The reason he left ANBU is from "The Mirror Cracked from Side to Side". Again, these have nothing to do with the anime arc, and they were all either planned out or written before it was even aired on TV.