Brainy orders a dozen pizzas, but leaves the shop with only five boxes.
Several times, L-Corp is referred to as "Luthor Corp", even though Lena officially had the company's name changed one year previously. (On the other hand, old habits do die hard.)
So, one little device, sitting on a table, is capable of seeding the entire atmosphere of the planet with krypton atoms, within seconds, faster than the speed of light would take to travel around the planet, and with high enough concentration to not only be measurable, but enough to effect Kryptonians across the entire planet? Ridiculous! And what happened to Superman during all of this? The writers really need to at pretend to address some basic science.
There is no way Mercy should have been able to hack Brainy's image inducer, as it's an advanced piece of technology from the 31st century, which he began using before L-Corp reverse-engineered it. Even assuming Brainy's inducer evolved from Lena's design, that in itself creates a bootstrap paradox: as a result of being brought back in time, it becomes the source of its own creation, and how it originally existed so that he could bring it back in time can't be determined.