I understand you are trying to create a ticket using Freshdesk REST API from C# code by following the GitHub samples. The samples written on GitHub illustrate a few basic options that can be performed, however, the API is not limited only to those fields.
The full set of API features can be found on our API Docs portal. For this specific use case i.e., create a ticket with cc-emails, custom fields and attachments kindly refer to create ticket API doc. It illustrates cURL options with API details. Kindly write equivalent C# client-side code as illustrated in GitHub, that should help.