Every company is different in terms of how they handle the interview process, but when it comes to companies like Facebook and Google, I have heard that knowing current employees is a big help especially if they have worked with you before. Besides that, I would say their process is differently not systematic enough that you can check off all the boxes and expect to get a job. There are many stories of people that are more than qualified than most people that did not land a job. They are large enough that they have that luxury.

I don't know your specific situation, but I would start talking ALOT with current employees, perfect your specific skills (be great at 1 thing, not ok at a lot), and keep trying :)

If you want to hop on a call I can help you with your specific situation. I have gotten pretty far in the interview process at Google, before I decided not to proceed and instead started my current startup Due.com.