I'm not sure knowing who is doing the hiring is going to help you - and there's no way to know whether they will take an application from a 17-year-old seriously. The only thing you can do is apply and keep applying whenever you see something that you could do. Even if it isn't your dream company, it gets you on location (where you'll hear about other opportunities) and into the industry (meeting people who can help you learn more).
I'd be surprised if anyone was upset at receiving two applications from you (one through agency and one through direct), it just shows that you are serious about finding work.
Good luck!