Creating address for sending transaction

Question

In a blockchain, every transaction is recorded. Lets say User A is sending money to User B.How to check if User A has sufficient balance, if User A is not using the same public address that was used when purchasing the coin.

My question:

We are able to create a address just for sending the transaction from User A to User B. It may be for anonymity purpose. How does blockchain check for balance in this case.

Will the creation of public key for transferring still be able to relate to original public key. if yes, in what ways?

Answer 1

Every account's balance and nonce are stored in a global database separated out from the blockchain (referred to as the World State in the whitepaper). The balance and nonce are verified against this when processing transactions to see if there are enough funds to complete the request.

See section 4.1 of the whitepaper for more details.