It won't hurt. And will probably help a little, but they suggest not using it until after the cycle since ammonia and Nitrite will leave the coraline spores dormant.
I used it after my cycle just for the hell of it since I used dry rock just to possibly help seed coraline.
You really don't need anything to start a cycle, nature will do its thing. And from what I've seen whether adding bacteria at the beginning or not cycles generally take the same amount of time.
No this is completely different product type, not a cycle starter. Per ARC this should be used when N03 is less than 5 ppm. So you have to wait until after the cycle is complete, and N03 is brought down. Also only buy when you’re ready to use. It must be used in 10 to 14 days, or something like that.