I've heard a number of suggestions of ways to "know" but I don't think any of them are proved reliable (and certainly nowhere near as reliable as a professional chicken sexer!)
There are markers and signs at about the 4 to 5 week mark, but only time will give you the 100% certainty. Especially with EEs.
Exactly.
Certain breeds can be fairly accurately sexed at hatch, but it's not 100% - but not EE's, they are crosses, so you never know what you're going to get.