Yes, you can, but you may need to adjust the amount of the other ingredients, especially liquids, because egg noodles are much larger than barley and will thicken your soup.

onion, sorrel, potato, broth, dill - barley and boiled egg is optional but sour cream when serving is a must!

Yes, barley is the correct spelling.

Some example sentences are:
He grows barley on his farm.
This barley bread is delicious.
Fruit and barley is a healthy snack.

Rice, wheat, sorghum, barley, millet, and sweet potatoes are Chinese staples.
stray cats

The collective noun for 'barley' is a crop of barley.