Who taught Goku the spirit bomb?

Many of Goku's signature techniques were learned while training under King Kai, the most notable being the Spirit Bomb that Goku has used consistently throughout the series, although usually without success. King Kai also taught Goku the Kaio-ken technique.

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Keeping this in consideration, why did goku's ki turn green?

The green in their aura is just to tease the LSSJ/Beserk form, which Broly gets in the movie. The green aura is actually the same blue aura in Dragon Ball Super, it was just animated differently so it looked better, and so the viewers would appreciate the power up more. Thereof, why is broly green? Before Broly transforms into a Super Saiyan in the film, there's a mid-tier transformation in which he taps into the power of the Saiyans' Great Ape form. Without his tail, he's allowed to gain this power and still keep him humanoid form, and this results in his green aura.

Accordingly, how did goku almost go ui in broly?

No. He never did. He explicitly stated in the end of the ToP arc in both anime and manga that he cannot use UI at will. Vegeta stated that it is a useless power if he cannot use it again. Correspondingly, why is kale like broly? Being his most recognized attribute, the similarities between their hair in Super Saiyan form are uncanny. They're both green with a particular pointed shape, and that's just one similarity. The color of her aura is also another indicator of Kale possessing some connection to Broly.

Regarding this, is broly a canon?

As Dragon Ball prepares for its next film, here's a look back at which anime movies in the franchise are actually canon. While the last film in the franchise, 2018's Dragon Ball Super: Broly, is canon to the overarching story, the vast majority of the franchise's films are not. Is Super Saiyan 4 furry? Vegeta's Super Saiyan 4 form In this form, the Saiyan's hair color differs, the same goes for the tail and the body is covered in red fur. All of which possess having very long black or dark colored hair, a reddish colored fur, and a red outline for around the eyes.