I'm starting a flip/flop at Harpers Ferry the last week of April. Before then I have to settle two questions:

1. Is there a definitive list somewhere of where one MUST use some sort of hard food protection (i.e. Bear Vault, Backpacker's Cache, etc.) on the AT?
Or is it still not mandatory on parts of the AT like it is on parts of the PCT?

2. I have never had a presence on any type of social media, but I'm considering changing that in order to keep friends/family up to date on my hike.
What I'm wondering is which platform do folks recommend for doing that? Obviously there would be photos (and possibly videos) involved.

Any opinions or information on the items above would be greatly appreciated.