@elulu8, I'm so glad you are enjoying Cats & Dogs ! 🐱🐶🥳 And I'm glad you got some extra money and that City Living was on sale! 🙌
To answer your question, the pack that came with friend groups was most likely the Get Together EP! It has a powerful Club system! I use the Garden Gnomes Club to tend my garden for free all the while earing club points while they are doing it! 😎 You can make your own clubs as well. There is also the possibility that the YouTube video you saw was the Discover University EP which has Organizations , but those will just be during the time your Sim is at university. 😉
I'm not sure if in Get to Work you can build on Sixam, since I have never tried to do so. Normally, you are only on Sixam during the work day (when traveling there is one of your daily tasks), so the time spent there is limited. But I have visited outside of work when my Scientist Sim has made a Wormhole Generator, and upgraded it and then cloned it so they could use the cloned one on their home lot! (You clone items with an object cloner that you make as a Scientist!) . When traveling to Sixam from home, I was able to stay there longer than while at work! I never tried building there , but you might be able to build there if you use the Free Build cheat! 🤔
Bring up the cheat box Ctrl + Shift + C
In the box type testingcheats true and hit Enter
Then type bb.enablefreebuild and hit Enter
This might allow you to build on Sixam. I know it allows you to build in university dorms and on with Realm of Magic it allows you to build in the Magic Realm! 🙌
Please update us on what you think about City Living, and about any other packs you get! Happy Simming! 🥳