Does if (child.isMesh) execute when the model is fully loaded?

Question 1) Does using if (child.isMesh) execute when the model is fully loaded?

Question 2) Assume it does wait untill the model is fully loaded how can we also wait for the textures ?

I suppose you will get a runtime error since child will be undefined until the model is loaded.

If you are using glTF, the onLoad() callback only fires if the entire model with all resources is loaded. If you load textures separately, you can use THREE.LoadingManager to track the loading progress of multiple loaders.