I’m oversimplifying this because it would take forever so don’t crucify me other lore people. 1.) Yes the black garden is likely the very same garden that the flower game took place in. Byf has a good video on it somewhere if you want the evidence behind it. I don’t believe it has been explicitly confirmed however. 2.) The vex are what won the flower game every, single, time. The gardener hated that the flower game because it essentially had no room for anything unique. Because the vex won, every, single, time. That is also why they are the only intelligent species in the garden currently. Because that is the playing field they have won in since time immemorial. 3.) The gardener changed the rules by adding itself to the game alongside the winnower. That added paracausality (actions that break the standard rules of the universe) has prevented the vex from winning like they always have before. However their sole goal continues to be the last living species in the universe. 4.) The vex struggle with paracausality because it can’t be predicted very well. They have won the flower game every time because alongside being a perfect unfeeling hive mind, their predictions were always correct. If you understand how the word works perfectly then even the future can be simulated exactly. Now they can’t do that, they try, and it works sometimes. But paracausal beings like guardians, and oryx give them particular trouble because they don’t follow the same rules everything else does. 5.) The vex have successfully worked with light and darkness to a very limited degree. The black heart was an “artificial” attempt at creating another veil like the one on neomuna. It worked but only partially, it created a connection with the traveler, but only substantially weakened the traveler instead of being capable of doing things like the witness did with the veil. They can also sorta understand the light. It took them absolute ages to do it, but they created a vex specifically tuned to saint 14s light which allowed them to kill him in the infinite forest. They haven’t done that with other guardians because they need a captive subject and an absolutely crazy amount of time to pull it off. In theory they could do it again but it would require a captive subject to study exactly how their light works. Which again, dosent make much sense to the vex so it takes them a long time. Bonus personal theory: The vex haven’t used heavy combat units because they don’t know how to win yet. Why would you start a fight you don’t know how to win? So they continue to do what they know best. To try and turn all the organic matter they can find into vex tech to be used for various purposes.