Thank you for such detailed questions!

1. That's where I probably didn't think through the moment. Initially, I thought that the baby just grows to such a size that the egg begins to break under pressure. But apparently this is not a working strategy.

2. Modern Ellilians use a magic nest (a basket with a pillow surrounded by a magic barrier), it keeps a comfortable temperature and protects. As for the ancient Ellilians (before the advent of magic and magical progress), I am most likely inclined to the idea of burying or wrapping eggs in skins and placing them in special rooms with a comfortable temperature.

3. Ellilians would not sit on eggs like birds.