When 3-year-old edward's dad asked his son what he had done that day, edward replied, "i sawed two deer outside and goed to see them." these classic language mistakes are called?

These simple language mistakes are known as grammar errors. Specifically, these grammar errors are word tense errors. In the above example, it was a past tense error wherein saw is already in its past tense so there is no need for an "ed" at the end. Also, "goed" should be "went" instead.