Will it really hire me ?
Solving a question in the long contest does not mean you will be recruited by Google, or any other Company. There are many users who can solve problems here. So , don’t get your hopes up.
But, if you compete in contests and are able to get a high score, then you might win cash prices.
And, by solving a lot of questions here, you can get better at programming, so, then, if you want to get a good job, then go for an interview or so, and if you are good enough, you can get selected.
If you could get into Google by solving one question from one long challenge, then almost any programmer could get into Google -_-
But a good start like that can certainly motivate you to put in some work and then be worthy of Google
Doing well in programming contests gives you a lot of interview opportunities, and also increases your chances for passing those interviews. However, it does not seems to be easiest/fastest way to get that job - you need to work hard and spend a lot of time to be good in contests, and by spending same time on focused preparation for interviews, on improving as a programmer (one who works on real projects, not a competitive one), you may reach much better results. So those job opportunities look like side effect of competitive programming.