Using hash values with stored personal data best enables an organization to detect changes to the data, because hash values are unique and fixed outputs that are generated from the data using a mathematical algorithm. If the data is altered in any way, even by a single bit, the hash value will change dramatically. Therefore, by comparing the current hash value of the data with the original or expected hash value, the organization can verify the integrity and authenticity of the data. If the hash values match, it means that the data has not been tampered with. If the hash values differ, it means that the data has been corrupted or modified.
Reference:
Ensuring Data Integrity with Hash Codes, Microsoft Learn
What is 'hashing,' and does it help avoid the obligations imposed by the new privacy regulations?, Data Privacy Dish

Encryption of network traffic is the most important control to mitigate the risk of potential personal data compromise when employees access corporate IT assets remotely. Encryption is a process that transforms data into an unreadable form, making it difficult for unauthorized parties to intercept, modify, or steal it. Encryption of network traffic ensures that the data transmitted between the remote employees and the corporate network is protected from eavesdropping, tampering, or leakage.
Intrusion prevention system (IPS), firewall rules review, and intrusion detection system (IDS) are also useful controls for network security, but they are not as effective as encryption for protecting personal data in transit. IPS and IDS can monitor and block malicious or suspicious network traffic, but they cannot prevent data exposure if the traffic is intercepted by a third party. Firewall rules review can help optimize and secure the firewall configuration, but it cannot guarantee that the firewall will not be bypassed or compromised by an attacker. Therefore, encryption of network traffic is the best option among the choices given.

Attribute-based access control (ABAC) is the best approach for limiting the access of regional HR team members to employee data only within their regional office, because it allows for fine-grained and dynamic access control based on attributes of the subject, object, environment, and action. Attributes are characteristics or properties that can be used to describe or identify entities, such as users, resources, locations, roles, or permissions. ABAC uses policies and rules that evaluate the attributes and grant or deny access accordingly. For example, an ABAC policy could state that a user can access an employee record if and only if the user's role is HR and the user's region matches the employee's region. This way, the access control can be tailored to the specific needs and context of the organization, without relying on predefined or fixed access levels.
Reference:
Attribute-Based Access Control (ABAC), NIST
What is Attribute-Based Access Control (ABAC)?, Axiomatics
Access Control Models - Westoahu Cybersecurity, Westoahu Cybersecurity

The best way for an organization to maintain the effectiveness of its privacy breach incident response plan is to conduct annual data privacy tabletop exercises. A tabletop exercise is a simulated scenario that tests the organization's ability to respond to a privacy breach incident in a realistic and interactive way. A tabletop exercise can help the organization to evaluate the roles and responsibilities of the incident response team, identify the gaps and weaknesses in the plan, improve the communication and coordination among the stakeholders, and update the plan based on the lessons learned and best practices12. A tabletop exercise can also enhance the awareness and readiness of the organization to handle privacy breach incidents in a timely and effective manner3. Reference:
ISACA CDPSE Review Manual, Chapter 4, Section 4.3.2
ISACA Journal, Volume 4, 2019, "Tabletop Exercises: Three Sample Scenarios" ISACA Journal, Volume 6, 2017, "Privacy Breach Response: Preparing for the Inevitable"