Check if Layer Exists (by name), Assign Gameobject to layer using LayerMask

check-layer.cs

// assign gameobject layer using layermask NOTE returns -2147483648 if you havent set the layermask in inspector!
go.layer = (int)(Mathf.Log((uint)layermask.value, 2));

// set layers to children also
foreach (Transform t in go.transform)
{
    t.gameObject.layer = (int)(Mathf.Log((uint)layermask.value, 2));
}

// check if layer exists by name
var newLayer = LayerMask.NameToLayer("MyLayer");
if (newLayer > -1)
{
  // we have it
}

Check if GameObject is in Layer or check if Layer is in LayerMask
https://gist.github.com/unitycoder/cb887da3be89458968101a92cf61720b