So what's happened to this app? Why is it not available anymore?

Hey guys I've been playing for a while, but recently got serious into learning how to be good at it! So I have a couple of questions for you: 1. I'm trying to figure out how best to learn which items compliment certain heros, as well as how to counter build your hero against the other team. Do you guys just memorize all the items or what?!? 2. I play Catherine a lot, and as a roam, i know I should be in charge of vision. How do you master that concept? What tips and tricks do you use to...