How does the game loop actually work?

Yeah i think I recalled that everyclass atleast gets called once per cycle? Like if it 120 frames unless it’s in some tick or special function it just gets called once every 120fps or 60fps etc etc. And is 4.15 a build I’m supposed to be using I’m running into alotttt of bugs… Where I think it’s my called but not and just have to reset the engine