Here is a very simple guide created by me it will help you on your boss fights B)
Hvolt
Difficulty: Easy Life bars: 2 Element: Thunder
Stategy: start by slashing his feet, then when he comes to the ground immediatly jump over him because he will dash in your direction. When he starts shooting mini light thingies at you jump in the middle or use Hx hair dash to jump upwards, continue the process and youl beat him quickly and get lv 4 :)
Leganchor
Difficulty: Easy/Medium Life bars: 2 Element: Ice
Strategy: Ok take advantage of model Fx and as soon as the battle starts get below him and shoot upwards with overdrive this will totally burn him and kill him super fast, when he throws those snake creatures dash and run and they will soon dissapear.
Purprill
Difficulty: Medium/Hard Life bars: 2 Element: None
Startegy: Ok this guy is really a pain if youre fighting him for the first time, so youl want to use Zx´s charged buster shot everytime he is grabbing on the rope thing, so that he falls and climbs the wall again, when he throws those tires, keep climbing the wall until he stops, then shoot, and shoot.