The account list is part of the instruction
The program never receives a loose pile of public keys. It receives the slice the instruction requested, in that order.
Guides
Notes from packets already used in the room.
These are the explanations we kept rewriting on the whiteboard until they matched the source. They follow the same shelf order as the reading room.
Seeds, the bump, and a signature the program can produce
A program has no private key. The seeds are how it still names an address only it can authorise.
Lamports that keep an account alive
An account stays alive because it holds enough lamports for its size, not because a calendar subscription is running.
Eight bytes before the fields
If you start parsing at byte zero, you are reading the discriminator and calling it a field.