like as we create a new block , so it will connected to existing Blockchain or it will create a new blockchain?
Yes, every block (except the first one) gives reference to the previous block, and it's not possible to change a part of the block without invalidating it.
To create an altcoin, you have two options:
1) Fork the blockchain by using
invalidateblock, which permanently considers a block and the following blocks invalid, then create your alternative chain.
2) Generate a blockchain starting from the genesis block.
Every block contains the hash of the preceding block in the header. It follows that you can go back block by block until you reach the genesis block.
This structure has a few interesting properties:
- Every block reconfirms all preceding blocks.
- There can only be a single block at the same height that is part of the most-work chain.
Sometimes, two miners succeed at the same time and publish two competing blocks at the same time. Since a new block can only commit to one predecessor, one of the two competing blocks will form a stale blockchain-tip that is not part of the most-work chain.