To configure additional redirection settings for requests to Frontend1 in Azure Front Door that have a header containing "string2" to be redirected to https://www.contoso.com/redirect2, the following actions should be performed:

Create a custom rule (B):
This action is necessary to define the specific condition for redirecting requests with the "string2" header to the desired URL.
Add a custom rule to Policy1 (C):
By adding a custom rule to Policy1, you can ensure that the redirection behavior is applied to requests passing through Frontend1 associated with Policy1.
Create an association (A):
Creating an association between the custom rule and the Frontend1 ensures that the redirection logic is correctly applied to requests with the specified header.

Explanation for other options:

Create a policy (D): This option is not required as Policy1 already exists and needs additional rules added to it, rather than creating a new policy.
Configure a managed rule (E): Managed rules are predefined rules provided by Azure for common security scenarios and are not directly related to custom redirection based on specific headers.
Create a frontend host (F): Creating a frontend host is not necessary for this scenario as the focus is on defining custom rules within the existing WAF policy for redirection based on specific headers.

Therefore, creating a custom rule, adding it to Policy1, and creating an association between the rule and Frontend1 are the appropriate actions to configure additional redirection settings for requests with "string2" headers in Azure Front Door....