Can Anyone Remove Blocks from A Blockchain?

Blockchain
#1

The way blocks are deleted from a blockchain is totally determined by how they are handled. It is not feasible to manually remove a block. However, if it is destroyed, the blockchain may attempt to rebuild the database with the help of other peers.

They can be deleted once they’ve been reviewed to shrink the blockchain’s size because they don’t require frequent operations. If required, it can be re-downloaded. Pruning is the term for this procedure.

#2

Possible, but somewhere between extremely difficult and practically impossible, depending on the blockchain.

The primary purpose of a blockchain implementation is to assure users that 1) the transactions that are recorded in a block are all valid, and 2) that those transactions can never be undone. That is the whole point of a shared ledger - to be an immutable (impossible to change) record.