> you can theoretically interview at each of the letters in FAANG every year
One of those letters will let you interview many times in a single year ;) (but not for the same role on the same team)
If I had any final advice for those intent on going through the interview meat grinder it is that while l33tcode can be useful, you'll still want to understand some of the why behind popular algorithms and not just have a ton of specific ones memorized. This will save you when you have to talk through a problem you're not already familiar with.
Skiena's The Algorithm Design Manual was more helpful to me than any other prep material in that regard.
I know you can interview at multiple roles at FB provided 1.) you pass the initial phone screen and 2.) the onsite loop is different - say, frontend vs. product/backend. Doesn't work for me this year since I likely failed the phonescreen...
I've heard in theory you can apply to multiple jobs at N too.