There are no limits on a public blockchain. Anyone with an internet connection can join the network and begin validating blocks and sending transactions. In most cases, such networks provide some sort of incentive to users who validate the blocks.
In any case, for transaction validation, this network often uses Proof of Work or Proof of Stake consensus algorithms.
You can download the protocol at any time in public blockchain architecture, and you will not require permission from anyone.
As a result, it is fully decentralized, with no single organization controlling the ecosystem. On the other hand, a private blockchain can only be edited and amended by the entity that owns it.
A public blockchain eliminated the need for a third party. The system has its own inherent flow, much like a moving river. The flow path is not controlled by anyone, but everyone uses it.
Why is public blockchain risky?
There is a possibility that a participant with, say, one bitcoin, may spend it twice and fraudulently get items worth two bitcoins before one of the providers of goods or services realizes the money has already been spent. However, this is a problem with any electronic money system and is one of the major reasons for clearing and settlement procedures in traditional currency systems.