I have recently got an E4 offer from Facebook / Meta. While I am awaiting my joining date, I was wondering about 2 things

1. What technology should I teach myself, so I can have a smooth transition to Meta. In effect what I am asking is for , what would be the 3 most common technology that I should teach myself while awaiting my joining. My background is in Java/spring-boot services. I read that PHP + Hack might be a good place - would it?
2. As a generalist software engineer, what are the typical teams that I will come accross in team matching? I am sure there are 100s of teams, but was wondering if somebody could list a bunch of them, so new joiners would have some anticipation of it. It would be good to know some info about the work-life-balance on the teams being mentioned, their size, tech stack, relative importance in the bigger picture of Meta, etc