disagree. to reverse something you gonna pretend on that your blockchain is right and other one is wrong.
That is not how bitcoin works. All the consensus rules are clearly defined and are enforced by each individual node. There is nothing to "pretend", the nodes will always follow the chain with the most amount of work.
Once a node validates a transaction, it propagates the transaction to other nodes in the network. If the majority of nodes in the network agree that the transaction is valid, it is added to a block of transactions.
That is not how bitcoin works.
Node verify transactions for themselves not for the network. The miner is also using its own node (or the pool that is using its own node) and if that node considers a single transaction that nobody else has seen or verified, it still can be added to the block they mine.
Once a block is added to the blockchain, it is considered confirmed. The confirmation process involves adding the block to the end of the blockchain and creating a unique hash that links the new block to the previous block. This hash creates an unalterable record of the transaction on the blockchain.
Not entirely correct. Confirmation is the other word for mining a block which is the process of finding a hash that is smaller than or equal to the target. The hash you find doesn't link the new block to the previous one, the fixed 32 byte hash inside the header that you mined is the link to the previous block.
The number of confirmations a transaction needs depends on the rules of the specific blockchain network. In general, the more confirmations a transaction has, the more secure it is considered to be, as it becomes increasingly difficult to alter or reverse the transaction with each new block added to the blockchain.
There aren't exactly any rules about number of confirmations in each cryptocurrency. It is more like the result of the other rules that exist in that cryptocurrency. For example an altcoin with "fast" blocks requires a lot more confirmations to have the same security. Or an altcoin with low hashrate that can be easily 51% attacked or a centralized altcoin with a mutable blockchain can never be secure no matter how many confirmations there are.