A few questions about harvest Moon Magical Melodies?

Lyla sells 2 things called Snowy Field and spring something. What are they? Why can't I use them? I bought them and it says I have no room for it and my house is upgraded to level 5 the last level, and there was NOTHING in my house. Also does the baby grow up into a child or is it going to be a baby that crawls and walks forever?