what is the difference between eatch coins wallet address,what is the coin public id/salt?
Yes, currencies like Bitcoin typically have a version byte that gets stored in the address which would be the PUBLIC_KEY_VERSION in the code you found.

More information here:

https://en.bitcoin.it/wiki/Technical_background_of_version_1_Bitcoin_addresses

https://en.bitcoin.it/wiki/List_of_address_prefixes

There is another byte used for private keys as well. See:

https://en.bitcoin.it/wiki/Wallet_import_format

These bytes can't really uniquely identify a coin but they should make it harder for users to accidentally send Bitcoin to a Dogecoin address or make other mistakes like that.