How should an associate display the sum of all closed won Opportunity amounts at the Account level?

Get Cloudy Consulting trains its new employee in a partial sandbox named New Employee; An employee competes the training in the sandbox and is ready to sign in to the production org. However, an error message pops ip indicating an invalid username or password. The employee is using their sandbox username and password to sign in to production.
What is needed to solve this error?

How should a Salesforce associate ensure a dashboard has the most current data?

A Salesforce associate deletes an Account of a company that recently went out of business.
Which other related records are automatically deleted?

Salesforce is built on objects like Account, Contact, and Opportunity.
What is a representation of an object?