You can't cancel a transaction. You can broadcast another transaction with a higher transaction fee (replace-by-fee) sending back to an address you own and hope that gets confirmed before the original transaction (miner is incentivized to mine this replacement transaction rather than the original one). Or alternatively you can ask the recipient to send the ...
In Mastering Bitcoin there is this diagram which shows the data included:
Previous Block Header Hash
Other sources indicate that the version number from the block header is also included in the data hashed.
The difficulty, which is loosely an inverse of the target, is in a compact representation known as "bits&...
No, because that would just result in miners stuffing their own blocks with back-and-forth transactions.
Every block has a finite amount of space (called "weight"), and every transaction has a certain weight based on its complexity. The sum of the weights of the transactions in a block cannot exceed 4000000. Transactions also each define a fee. ...