You're very welcome. Thanks for the questions.
1) I try to only give advance for things I feel like I'm adequately educated on. Testing isn't one of them. I usually redirect all the testing questions I get on testing to Kent C Dodds. He has a special kind of love for testing.
2) Expo is more of a toolchain rather than a library but it's so good I'm going to cheat and pick that as my first choice. Second is React Router. Do I think it's ready for production React Native apps? No. But I LOVE React Router on the web and I think with a dedicated animations lib, it could shine on native too. Third, react-native-vector icons for obvious reasons. Fourth, React Native Router Flux. I started using this project really early. Like, really really early (github.com/aksonov/react-native-router-flux/issue…). At the time I didn't love it but it's grown a LOT since then and even though I don't personally use it, I think it deserves more love than it gets. Last is react-native-hyperlink because it's simple and does what it says it does.
3) Oh man that's a big question. It started off with just writing blog posts. What I found was that if I really wanted to learn something, the most effective (and quickest) way to do that was to write about it. This is still the foundation of anything new I learn. I try really hard to minimize the time between learning a thing and writing about it. There are a few people who hate on this model because apparently only experts should have permission. I think their intentions are pure but I strongly disagree with their premise. From there I spoke at a few meetups and found that I really enjoy talking about technical topics as well. At that time I met John Lindquist (from Egghead fame) at a meetup. They helped me get my start with screencasting (for which I'm so grateful. Love egghead). I did that for about a year then decided to go out on my own to get a little more freedom. And, now we're here.
4) That's actually a pretty old picture and both the laptop and the hair is gone. My current laptop looks like this (you can go here to get a free sticker too) - https://tylermcginnis.com/sticker