My english is not very bad, I used Google Translator: If the Scratch does Skaia exchange portals of Reckoning, and Karkat who made Ectobiology experiments, such as the Pre-Scratch Trolls activated Scratch if they not did ectobiology experiment? Or did they?

They did not. Part of the reason they needed to Scratch was because they hadn’t made themselves.  In other word: They needed to scratch in order for them to be born