Most supplements do not need to be cycled. That’s sort of a leftover phrase from the prohormone days. If any Biotest supplement needs cycled (Alpha Male come to mind), the label will say so.
Now, some people make a false assumption when it comes to certain supplements. They think “my body got used to it” so they cycle off, then get back on to “feel it” again. But the supplement was always working and doing its thing – they just got used to it psychologically, but not physiologically, if that makes sense.
It’s smart to not overuse things like stimulants of course. That’s something you can adapt to – there’s a point where adding more and more just doesn’t do anything for you and you start to backslide.
Carb/protein cycling is another matter, a diet issue, and you’ll find smart experts on both sides of the fence on those issues, with dozens of different theories and diets based on them. I’ve also noted that when you use proper workout nutrition, such as Plazma, you are carb cycling in a sense because you don’t use it on non-lifting days, hence naturally cycling carbs.
As for your other questions, you probably don’t need extra BCAAs if you’re already using Plazma and Mag-10. Adding creatine is perfectly fine if you respond well to it, and you can add it right into things like Plazma, Surge or Mag-10.