Successfully completing a scenario in The Sims 4 rewards the whole household with several thousand Satisfaction Points apiece. What are the rewards for completing a Scenario? I haven’t had a chance to test it thoroughly yet, but there don’t seem to be any limits on how many concurrent Scenarios you can have. You can have multiple active Scenarios in the same save. When viewing your Saved Games list, you’ll see the flag icon on the thumbnail denoting that there’s an active Scenario in the save. However, you only progress through the Scenario whenever you switch back to playing with the founding household. While playing a save with an active Scenario, you can switch to other households and play as them without cancelling the challenge. You can also cancel the Scenario from here if you choose to, with no penalty (other than the fact that you’ll need to create a new household from scratch if you decide to restart later). Once your household is created and moved in, you can view or hide the victory conditions for the active Scenario by clicking the little flag icon in the upper left hand corner of the Live Mode screen. Either way, you’ll be taken to Create-A-Sim, where you create a brand-new household to play the Scenario. From here there are two options: Start in a New Save or Start with Existing Save.
Click View on a Scenario to see its starting and victory conditions.
Clicking this button will bring up a menu of all currently available Scenarios.