AWS Certified Security - Specialty

An organization wants to deploy a three-tier web application whereby the application servers run on Amazon EC2 instances. These EC2 instances need access to credentials that they will use to authenticate their SQL connections to an Amazon RDS DB instance. Also, AWS Lambda functions must issue queries to the RDS database by using the same database credentials.
The credentials must be stored so that the EC2 instances and the Lambda functions can access them. No other access is allowed. The access logs must record when the credentials were accessed and by whom.
What should the Security Engineer do to meet these requirements?

A company has a customer master key (CMK) with imported key materials. Company policy requires that all encryption keys must be rotated every year.
What can be done to implement the above policy?

A water utility company uses a number of Amazon EC2 instances to manage updates to a fleet of 2,000 Internet of Things (IoT) field devices that monitor water quality. These devices each have unique access credentials.
An operational safety policy requires that access to specific credentials is independently auditable.
What is the MOST cost-effective way to manage the storage of credentials?

An organization is using Amazon CloudWatch Logs with agents deployed on its Linux Amazon EC2 instances. The agent configuration files have been checked and the application log files to be pushed are configured correctly. A review has identified that logging from specific instances is missing.
Which steps should be taken to troubleshoot the issue? (Choose two.)

A Security Engineer must design a solution that enables the incident Response team to audit for changes to a user's IAM permissions in the case of a security incident.
How can this be accomplished?