Bro,
Thats not a button. That looks more like a gonio.
The best way to test if your tank is ready for livestock is by testing the water parameters using testkits and not using live fishes. Damsels are quite hardy fishes and can tolerate poor water parameters. 8 days cycling period is abit short, do monitor your fishes and corals closely. Also, stock up very slowing since you have a small water volume. Try to limit the number of livestock since 24G is not really not big volume. If you are not running a skimmer, do consider to put in more live rocks to help with the nutrients breakdown.