As mentioned in question 1, the SOW describes the specific activities, deliverables, and schedules for a penetration tester. The other documents are not relevant for this purpose. An NDA is a non-disclosure agreement that protects the confidentiality of the client's information. An MSA is a master service agreement that defines the general terms and conditions of a business relationship. An MOU is a memorandum of understanding that expresses a common intention or agreement between parties.

The scoping document is a document that defines the objectives, scope, limitations, deliverables, and expectations of a penetration testing engagement. It is an essential document that guides the penetration testing process and ensures that both the tester and the client agree on the terms and conditions of the test. Requiring all testers to review the scoping document carefully would have most effectively prevented this misunderstanding, as it would have informed the new tester about the client's request not to test the production networks. The other options are not effective or realistic ways to prevent this misunderstanding.

The /var/log/lastlog file is a log file that stores information about the last user to sign in to the server. This file stores information such as the username, IP address, and timestamp of the last user to sign in to the server. It can be used by a penetration tester to determine the identity of the last user who signed in to the web server, which can be helpful in identifying the user who may have set up the backdoors and other malicious activities.

https://nmap.org/book/scan-methods-ack-scan.html

Open-source research and traffic sniffing are two activities that have a minimal chance of detection, as they do not involve sending any packets or requests to the target network or system. Open-source research is the process of gathering information from publicly available sources, such as websites, social media, blogs, forums, etc. Traffic sniffing is the process of capturing and analyzing network packets that are transmitted over a shared medium, such as wireless or Ethernet.
Reference: https://www.sciencedirect.com/topics/computer-science/passive-reconnaissance