You can't, I think

To age down you need to have your fishing and cooking skill really high, preferably maxed
out.Then go to the book store to learn ambrosia it's a 12,000 Sim$ recipe.Go to the
graveyard past midnight and fish to get Death Fish, and look around the grave yard for a
life seed,this is how to get the ingridients for ambrosia(on Sims 3 :P). hoped this helped
:)

i think if u use a death flower found in the grave yard u might be able to

how the hell do u do that

Why do you even want to age down? It's ***, because you can't do it in real life. The
Sims 3 is meant to be as realistic as it can.

hold in ctrl+shift+c together and type in setAge 6 and your sim will be a child!!

by *** off

ha ha ha, already done it via modding

& i can spawn ambrosia without making it.