Can Blocks be reorganized in the blockchain

Question

Can a invalid transaction be stored on the Blockchain. What happens when blocks are reorganized and transactions gets reverted, is the record of the transaction still stored even though it has been deleted.?

Answer 1

In practical applications, invalid transactions can not be stored on blockchain because there are validating nodes who check for the validity and genuineness of the transaction. But, there a possibility that an invalid transaction can be stored on the blockchain when 51% (or more) of validating nodes approve an invalid transaction.

The blocks of a blockchain can not be re-organized and the transactions can not be reverted. The main intention/feature of Blockchain is that the data in it can not be altered and hence re-organization of blocks are is not possible.

So to answer to your question in a practical scenario,

1. No, invalid transaction be stored on a Blockchain.
2. You can not re-organize or revert transactions on a Blockchain.