Q: Do you want me to configure authentication to the entire OSPF network?
A: Refer to your text. The question is concerned about a specific part of your OSPF network. Configure the way you think will be best to accomplish it.
Q: I am thinking I have different ways to accomplish the Telnet restriction on Sw2. Is there a preference for which approach to take?
A: Any approach is fine as long as you configure a solution that meets the criteria.