Did Shen began to use fireworks years before the panda massacre?

In Kung Fu Panda 2, Shifu mentioned Po found inner peace at such a young age. However, Shen waited 30 years to rule over Gongmen City alongside his cannon which he envisioned probably since then he started to use fireworks as a weapon not years before he attacked the panda village and it's not even mentioned or shown that Shen began to use fireworks as a weapon years before or it was less than 30 years ago he attacked the panda village and was exiled. But in Kung Fu Panda 3 Mr. Ping mentioned that he raised Po for 20 years before Mr. Ping told him he was adopted and according to director Jennifer Nuh Nelson Po is in his 20s and in Secrets of the Scroll he was teenager 10 years ago?