Learning more and deeper about crypto/blockchains, community, security, and development

Hi everyone,

Currently I have only been holding BTC and ETH, and now I want to learn more about crypto and blockchains in general. So I was wondering if you could help me with some questions:

1. I have heard that "Mastering Bitcoin" and "Mastering Ethereum" are good. If you have read them, which one would you prefer and recommend?
2. Security is a big part of blockchain, for instance, sometimes I heard that people's wallets were hacked. So I was wondering if you have any recommendations for books or blogs on the security aspects of crypto/blockchain, such as how to avoid being hacked and how attacks were organized?
3. Other than this sub and some people on Twitter, do you have any recommendation for other communities that have quality information and discussion?
4. Lastly, are there any educational resources on managing airdrops with programming? Is it closely related to development mentioned in the Mastering books?

Thank you for your time!