GerberGerber Baby Girls 4 Pack 'N Play Footie And Toddler Sleepers, Lavender Garden, Newborn US

What time of year are these best worn in? Thanks

The picture shows mittens cuffs so do they have mittens on them???

What time of year are these best worn in? Thanks

What are the preemie size height and weight? The size chart starts at newborn and doesn’t include preemie.