The best option for the tester to take is to notify the client about the firewall. The firewall is not part of the original list of IP addresses for the engagement, which means it is out of scope and should not be tested without permission. The tester should inform the client about the existence and potential risks of the firewall, and ask if they want to include it in the scope or not.

Quarterly is the minimum frequency to complete the scan of the system that is PCI DSS v3.2.1 compliant, according to Requirement 11.2.2 of the standard1. PCI DSS (Payment Card Industry Data Security Standard) is a set of security standards that applies to any organization that processes, stores, or transmits credit card information. Requirement 11.2.2 states that organizations must perform internal vulnerability scans at least quarterly and after any significant change in the network.
https://www.pcicomplianceguide.org/faq/#25
PCI DSS requires quarterly vulnerability/penetration tests, not weekly.

The open port 2049/tcp indicates that the Network File System (NFS) service is running. NFS is commonly used for file sharing in Unix/Linux environments. If not properly secured, NFS can be vulnerable to a variety of attacks, such as unauthorized access to shared files and directories, or privilege escalation by exploiting misconfigurations or vulnerabilities within the NFS service. This makes it a prime target for attackers.

Cross-Site Request Forgery (CSRF) vulnerabilities can be leveraged to trick authenticated users into performing unwanted actions on a web application. The right tool for this task would help in exploiting web-based vulnerabilities, particularly those related to web browsers and interactions.
BeEF is a powerful tool specifically designed for exploiting web browser vulnerabilities. It can hook web browsers and perform a wide range of attacks, including CSRF. Capabilities: BeEF is equipped with modules to create CSRF attacks, capture session tokens, and gather sensitive information from the target user's browser session. Reference: BeEF is widely used in penetration testing for its extensive capabilities in exploiting web application vulnerabilities and manipulating browser sessions.