How can the developer incorporate the list of approved instance types in the CloudFormation template?

Explanations:

Creating a separate CloudFormation template for each EC2 instance type is inefficient and not scalable, as it would require managing multiple templates for different instance types, increasing complexity and maintenance overhead.

Defining resources for each EC2 instance type in the Resources section would lead to a template that lacks flexibility. It would not allow the user to choose from approved instance types at runtime, making the template less dynamic and adaptable to changes.

Creating a separate parameter for each EC2 instance type would clutter the template with numerous parameters, making it unwieldy. Additionally, this approach does not restrict the choice to the list of approved types effectively and can lead to confusion during deployment.

Creating a parameter with the list of EC2 instance types as AllowedValues allows the user to select from a predefined set of approved instance types. This ensures that only valid options are chosen at deployment time, promoting best practices and maintaining compliance with organizational policies.