I have a problem (load scene async)?

Unity Engine
1

when I write:

 asyncOp=SceneManager.LoadSceneAsync(0);
asyncOp.allowSceneActivation = true;
asyncOp=SceneManager.LoadSceneAsync(1);
asyncOp.allowSceneActivation = false;

it is ok and it loads scene0 but when I write :

SceneManager.LoadScene(0);

asyncOp=SceneManager.LoadSceneAsync(1);
asyncOp.allowSceneActivation = false;

I have aproblem , It loads scene1 !!! why

2

From where do you call these? There was a bug, where calling these from Awake or Start caused LoadSceneAsync to not be async and it would ignore the “allowSceneActivation” parameter. I had to do the loading in Update (only once of course). Not sure if this has been fixed or not.

3

All have been written in update for only one time.
one: using LoadSceneAsync for two scenes, it is correct
two: using loadScene and LoadSceneAsync . it is incorrect. why?!!

I want to load the first scene and preload scene2.