It's not a big deal, when she goes through her first mini molt at around 12 weeks old her feathers will probably grow in like the others. Sometimes there are just genetic malfunctions also.
That's a tough one. Could you post a pic of the tail feathers? If they are rounded, it's a girl. If they are long and pointed, it's a boy. I am leaning towards boy but hard to tell.
Look like ISA Browns crosses, which means they would be easter eggers. They have a pea comb, but no muffs or beard which means they must be easter eggers.