* You don't have to use 4-5th grade level English for our sakes. It might force you to explain things better though.
* When answering the question about the most impressive thing you've achieved, it's not necessary to "focus on things that can be useful in a startup." In fact that's a common mistake. If you won an Olympic gold medal and can also write hello world in Ruby, we want to hear about the former, not the latter.
* How you hacked some real-world system to your advantage is not a super important question. Probably not even in the top 10.
I don't know about the other YC partners, but the two most important questions to me are what you've done in the past that's impressive, and why you chose the idea you're working on.
The biggest mistake founders make when applying is to confuse us. Half the time when I'm reading an application I'm thinking "I have no idea what this person is even talking about." I suspect this often the writer's own confusion showing through.
It's surprisingly hard to explain oneself. Even startups that we've accepted and have spent months working with say things in draft Demo Day presentations that make me ask "what does that even mean?"