@Hari Sheth Thank you for reaching out to us, As I understand you are trying to create a custom Azure AD role with the following permissions
microsoft.directory/users/authenticationMethods/create
microsoft.directory/users/authenticationMethods/delete
microsoft.directory/users/authenticationMethods/basic/update
Above permissions are defined in the Built in roles itself, these permissions are not available for the custom role.
As per this https://learn.microsoft.com/en-us/azure/active-directory/roles/custom-user-permissions only these user permissions are available for custom role.
You can share your feedback on https://feedback.azure.com/d365community to have more user specific permissions for custom role with business justification, as this feedback is closely reviewed by our product team.
Let me know if you have any further questions, feel free to post back.
Please remember to "Accept Answer" if answer helped, so that others in the community facing similar issues can easily find the solution.