A duckling raised alone will imprint on its owner instead of ducks. When grown it will not relate to other ducks in any way. You can prevent this by raising the duckling with chicks. When mature, the duck will bond with other ducks. I've done this nd know it works.
The egg in the picture has died and needs to be removed. When eggs die, gases build up and eventually break or explode; this may destroy other viable eggs. Be careful when you discard the egg so it does not break.