The only one to actually have an actual aspiration attached was the Positivity Challenge. The others were just challenges that you unlocked rewards when you completed the goals of the challenge (which were all collection based) there were no traits associated with them. The Collections attached to the Day of the Dead, Easter Egg and the Plant Sim Challenge can now be obtained through various Seasons events/traditions (Egg Hunt is it's own Tradition, I believe you can get Sugar Skulls through the Remberance Tradition and seeds/beans for the plantsim challenge drop in the Rare seed packets) but the unlocks for completing those events only are available using the cheat.
For the Positivity Challenge you won't be able to re-add the aspiration but you should be able to add the trait using the Equip Trait cheat. To do so: Open the Cheat Menu, Type testingcheats true (or testingcheatsenabled true), and then enter traits.equip_trait kindness ambassador
I'm guessing the Motivational poster collection will still be locked unless you use the cheat though.
