Call a method from all GameObjects implementing a specific interface in Unity
In the first loop I think, you could do:

if (projectiles.Any(p =&gt; p.IsActive))
{
  return;
}




In the second you could do something like:

foreach (var currentComponent in sceneObjects.Select(so =&gt; so.GetComponent&lt;IRewindable&gt;()).Where(r =&gt; r != null))
{
  currentComponent.Rewind();
}


But be aware, that using linq is not necessarily the most optimized approach (performance wise) , so you'll have to do some tests.