Yes you can eat it, the older and larger it gets, the tougher the skin is the general rule. Most squash tastes best while still young and small, this is true for most green and yellow varieties. Older, larger squash is best when split, buttered or stuffed, and then baked. You can peel it, cut it up and steam it for a tasty treat. Not knowing which variety you are referring to. I really can't add much more to this but you can freeze any squash if it is properly prepared for freezing