In my further understanding, I know that blockchain is not only limited to public blockchain like how bitcoin do, blockchain can also limit to private or even hybrid. Like how I know some ICO about blockchain on medicals are indicating that the person like doctors, nurse can have the permission to access your medical data, so no matter where you are, your medical record is still one and comprehensive.
Correct. But you have to deal with the privacy/information security issue here, so either lock the data up in independent databases and just keep hashes on the blockchain, or use a privacy-friendly technology such as ZCash.