How is a transaction public key related to original public

Question

When a transaction is made from one user to another user, a key is generated. Suppose one user initiates a transaction and has insufficient balance, how will the other user know that this user has insufficient balance? How is the transaction public key linked to the original public key? Is it possible to trace back to the original public key from transaction public key.

Answer 1

I'd also like to know where is the account balance info stored

Answer 2

The details like account balance, nonce etc., are stored in the global database. This global database is not included in the blockchain. When a transaction is initiated, the nodes in the network verify the balance and nonce to see if there is enough balance to make the transaction. If yes, then the transaction is made.