WELAKENGirls Sweatshirts Long Sleeve Pullover Crewneck Tops Shirts

I am buying as a gift for out of town niece and she wears size 10-12 in little girls. What size would work for this?

There are no washing instructions inside shirt. Amazon site says machine wash. Is it machine wash col? Is it tumble dry low or line dry?

Would this be suitable for 40°F to 50°F degree weather?

Why with the colors of LGBT xxv cucumbers?