A: Not from the add or update itself. Adding a company from Company Data Hub, or updating an existing company from it, fills in company details such as address, organization number, turnover and number of employees, but not credit rating. Credit rating comes from credit monitoring.
An administrator chooses which companies are credit monitored under Settings → Account → Business rules → Credit monitoring by selecting company list views. Credit monitoring requires the Company Data Hub add-on. When a company you add or update matches one of the selected list views and can be monitored, it gets its credit rating the next time credit monitoring runs. This happens every hour.
For which companies can be monitored and how to set it up, see Credit monitoring: How it works.