A top-down maturity model process is a method of assessing and improving the maturity level of a process or a set of processes within an organization. A maturity level is a measure of how well-defined, controlled, measured, and optimized a process is. A top-down maturity model process starts with defining the desired maturity level and then identifying the gaps and improvement opportunities for each process. This helps prioritize the processes that need the most attention and improvement. Therefore, a result of utilizing a top- down maturity model process is identification of processes with the most improvement opportunities.
A means of benchmarking the effectiveness of similar processes with peers, a means of comparing the effectiveness of other processes within the enterprise, and identification of older, more established processes to ensure timely review are not results of utilizing a top-down maturity model process. These are possible benefits or objectives of using other types of maturity models or assessment methods, but they are not specific to a top-down approach.

The best way to provide assurance of the integrity of a firewall log is to ensure that the log cannot be modified. A firewall log is a record of the traffic and events that occur at the firewall, which is a device or software that controls and filters the incoming and outgoing network traffic based on predefined rules and policies. The integrity of a firewall log means that the log is accurate, complete, consistent, and valid, and that it has not been altered, deleted, or corrupted by unauthorized or malicious parties. The IS auditor should verify that the firewall log has adequate controls to prevent or detect any modification of the log, such as encryption, hashing, digital signatures, write-once media, or tamper-evident seals. The other options are not as effective as ensuring that the log cannot be modified, because they either do not address the integrity of the log data, or they are monitoring or retention measures rather than preventive or detective controls. References:
CISA Review Manual (Digital Version)1, Chapter 5, Section 5.2.4

The most effective control over visitor access to highly secured areas is to require visitors to be escorted by authorized personnel. This control ensures that visitors are supervised at all times and do not enter any restricted or sensitive areas without permission. It also allows authorized personnel to verify the identity, purpose, and clearance of the visitors, and to monitor their behavior and activities. Escorting visitors also reduces the risk of tailgating, piggybacking, or unauthorized duplication of access credentials.
Requiring visitors to use biometric authentication, monitoring visitors online by security cameras, and requiring visitors to enter through dead-man doors are all examples of technical controls that can enhance visitor access control, but they are not as effective as escorting visitors. Biometric authentication can provide a high level of identity verification, but it does not prevent visitors from accessing unauthorized areas or compromising security in other ways. Security cameras can provide a record of visitor movements and actions, but they may not deter or detect security breaches in real time. Dead-man doors can prevent unauthorized entry by requiring two-factor authentication, but they do not ensure that visitors are accompanied by authorized personnel.
References:
ISC Best Practices for Facility Access Control1
Visitor Management Best Practices From Top Organizations2
8 Best Practices for Setting Up a Visitor Management System3

A mirror backup is a type of backup that creates an exact copy of the source data to the destination, without using any compression or encryption. A mirror backup is the best backup scheme to recommend given the need for a shorter restoration time in the event of a disruption, because it allows for the fastest and easiest recovery of data. A mirror backup does not store any previous versions of the files, so it only reflects the current state of the source data. Therefore, a mirror backup requires less storage space than a full backup, but more than an incremental or differential backup.
A differential backup is a type of backup that stores the changes made to the source data since the last full backup. A differential backup requires less storage space and time than a full backup, but more than an incremental backup. However, a differential backup also requires more time and resources to restore than a mirror or full backup, because it needs to combine the last full backup and the latest differential backup to recover the data.
A full backup is a type of backup that copies all the files and folders from the source data to the destination, regardless of whether they have changed or not. A full backup provides the most complete protection of data and the simplest recovery process, but it also requires the most storage space and time to perform. A full backup is usually done periodically, such as weekly or monthly, and followed by incremental or differential backups.
An incremental backup is a type of backup that stores the changes made to the source data since the last backup, whether it was a full or an incremental backup. An incremental backup requires the least storage space and time to perform, but it also requires the most time and resources to restore, because it needs to combine all the previous backups in chronological order to recover the data.