Blocks crypto mining

Whats going on with blockchain

How are blocks added to a bitcoin transaction would take.

Where can you buy sandbox crypto

If the output transaction is missing for any input, this will be an orphan transaction. For a hacker to make the entire blockchain valid for the block B that has been changed, he or she would have to change the hash value of all the blocks ahead of block B. It will take on average more than quadrillion hash calculations per second for the network to discover the next block.