How do i become a young adult again in sims 4?

Yes you can by doing this open the cheat box press shift-ctrl c then type in boolprop testingcheatsenabled true then shift click on a sim and press "Spawn" then you press "Sim Modder" a standing up newborn baby should show up next to your sim then click on the baby there will be an aging option it will ask you who you want to age and how old you want to be *Notes* if you want your sim to be a baby (or toddler) they may be able to do adult things and if your a child (Teenager) the sim's grade will be "F"* your sim will have a quick birthday becoming the age division you choose it to be I hope this helped..... Enjoy! :)