The abilities should be
quicker learning skills like (sports, programming, logic, painting, etc.) more skills then child and less skills then teen
childish midlife crisis or otherwise puberty behavior (mood changing often)
love interactions like hug, kiss on cheeks, first kiss, kiss, holding hands, watching stars, innocence flirting (not sexual flirt), and being boyfriend/girlfriend) or nowedays bg bb gg
sexual blocking script for modders no pedophilia actions possible like preteen and (young adult-elder) only to preteen, themselve or max teen. but that's modding not ea or maxis
playing with toys for their age like Lego, Knex,HotWheels, Console/pc, sports (more then the child can do) so they can make it into an stuff pack or update
and i din't say about the awkward stuff like acne or private parts (their just barbie dolls so they don't have any only with mods but that are mods) and they have mosaic around them if you don't have the decencor mod
puberty behavior is different from a 13year old and a 16+year old because childish ----- adult (adult childish is still different then child childish)
child in game is around age 8 ---- preteen could be around age 12 ---- teen is 16+ because they can work and you need to be atleast 16 for work or drive cars (sims 3) that means thats the gap from 8 years is spitted in half 4 years 4years, that's also visual in length so the preteen should be in size head bigger then child and head smaller then teen