Not sure if you’re joking but is it possible to even do that? I understand some books are kept on their cloud servers and only some get downloaded.
I had an old kindle that I never connected to the net or with an amazon account. I loaded books by USB.
Damn near impossible to find DRM free books to purchase though.
No, you choose what is downloaded locally. You can also get .mobi files and copy them to the kindle directly.
Yes, it’s possible. Note: no downloads work in airplane mode. Cable works just as well though.