Hudson BabyUnisex-Baby Cozy Fleece Booties

Is there a size chart that shows what shoe size corresponds with the month size listing or the approximate length of baby's foot for the 0-6 & 6-12?

Can these be worn in summer or are they too hot?

Are these secure for babies who like to take socks off?

What is the difference between 6-12 month and 6-12 months infant?