You're welcome
@Snoochenpurner. I typed this response before I saw your response, Metro.
Short lifespan is what we use for challenges --- in a brand new game file with a brand new Sim (or Sims, depending on the challenge.)
At the top of each challenge, there is a link to the general rules, as well as the rules for each specific challenge.
To get to the game options menu:
Start a new game
In Create-A-Sim (CAS for short)
Go to the "three dots" in the upper right corner (options menu), and select game options from the menu, which will come up.
Then, in the list at the left side of the game options screen, select "gameplay."
When you get to gameplay, full autonomy, auto age played Sims (select "yes" from the drop-down menu) and auto age unplayed Sims needs to be checked off and select short lifespan from the drop-down menu,