Any of these 3 actions is considered an attack. The more energy it takes to perform an attack, the greater the security of the blockchain. Remember that a true-blockchain is just a series of single question math contests where the chain security increases as the competition grows stronger, and vice versa.

I vividly agree to this quoted text of yours
Blockchain is a greater accuracy of numerics pragmatically.
Sadly, some folks are only enthused with Bitcoin and are yet to understand the concept or theory backing it.
Bitcoin popularized Blockchain though but the later is the powerhouse and lifeline for the survival of the former and Cryptography.
In essence, Blockchain verifies the belief that there is power in numbers