I own better language apps that help you understand grammar by explanation. Unfortunately, this app has NO EXPLANATION OR EXAMPLES. Every test question should have a brief blurb on what makes it the best choice, rather than assuming it sounds best.
In addition, a program on proper grammar should not have grammatical ERRORS. You cannot trust a company who doesnt go through their product to correct mistakes.
Overall, I would not invest $$ in the full version. Its an app with various tests without explanation - and every teacher knows that if you dont explain or show examples, then a student doesnt learn.
Lea11, Hawaii about Grammar Up : 1800 Questions