Garbage Skills Become the Strongest In the Ninja World

The first version, Tv339 episode, Kakashi was 12 years old and became a shinobi. The Minato team performed the mission of Kamabashi Bridge. During the mission, Minato said that Hatake Sakumo died 5 years ago. According to this version, Kakashi died at the age of 7.

These episodes are "Kakashi Gaiden", also in the manga, serialized between the first and second parts.

The second version, the Book of Fighting.

In the book of fighting, Kakashi is 27 years old, and it is mentioned that the battle of Kamabashi Bridge was 13 years ago. According to this version, Kakashi was 14 years old at the time, and 14 years old and 5 years old is 9 years old.

In this version, Kakashi died at the age of 9.

The third version, tv636 episode.

Obito hadn't graduated yet, and after hearing from passers-by that Kakashi was difficult to get along with, he remembered that Kakashi's personality had changed a lot the last time they met.

Sandai arranged for Minato to be Kakashi's tutor, and revealed the death of Hatake Sakumo. Soon after, Obito graduated and joined Watergate's team.

This episode is an original animation.

Of the three versions I know of, none of them say that Kakashi died before graduation. Sakumo died when he was about 7-9 years old.